MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Molecular Microbiology' source. Mon, 06 Feb 2012 21:32:20 +0100 http://www.medworm.com/index.php?rid=5664653&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07973.x SummaryThe Escherichia coli Adhesin Involved in Diffuse Adherence (AIDA‐I) is a multifunctional protein that belongs to the family of monomeric autotransporters. This adhesin can be glycosylated by the AIDA‐associated heptosyltransferase (Aah). Glycosylation appears to be restricted to the extracellular domain of AIDA‐I, which comprises imperfect repeats of a 19‐amino‐acid consensus sequence and is predicted to form a β‐helix. Here, we show that Aah homologues can be found in many Gram‐negative bacteria, including Citrobacter rodentium. We demonstrated that an AIDA‐like protein is glycosylated in this species by the Aah homologue. We then investigated the substrate recognition mechanism of the E. coli Aah heptosyltransferase. We found that a peptide corresponding to one ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5664653 Sun, 05 Feb 2012 05:00:00 +0100 5664653 http://www.medworm.com/index.php?rid=5657234&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07982.x SummaryThe redox‐regulated chaperone Hsp33 protects bacteria specifically against stress conditions that cause oxidative protein unfolding, such as treatment with bleach or exposure to peroxide at elevated temperatures. To gain insight into the mechanism by which expression of Hsp33 confers resistance to oxidative protein unfolding conditions, we made use of V. cholerae strain O395 lacking the Hsp33 gene hslO. We found that this strain, which is exquisitely bleach‐sensitive, displays a temperature‐sensitive (ts) phenotype during aerobic growth, implying that V. cholerae suffers from oxidative heat stress when cultivated at 43°C. We utilized this phenotype to select for E. coli genes that rescue the ts phenotype of V. cholerae ΔhslO when overexpressed. We discovered that expression ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5657234 Thu, 02 Feb 2012 05:00:00 +0100 5657234 http://www.medworm.com/index.php?rid=5657233&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07983.x SUMMARYStreptomyces coelicolor is a multicellular bacterium whose life cycle encompasses three differentiated states: vegetative hyphae, aerial hyphae and spores. Amongst the factors required for aerial development are the ‘chaplins’, a family of eight secreted proteins that coat the surface of aerial hyphae. Three chaplins (the ‘long’ chaplins, ChpA, B and C) possess an LAXTG‐containing C‐terminal sorting signal and are predicted sortase substrates. The five remaining ‘short’ chaplins are presumed to be associated with the cell surface through interactions with the long chaplins. We show here that two sortase enzymes, SrtE1 and SrtE2, cleave LAXTG‐containing peptides at two distinct positions in vitro, and are required for cell wall anchoring of ChpC in vivo. srtE1/E2 do... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5657233 Thu, 02 Feb 2012 05:00:00 +0100 5657233 http://www.medworm.com/index.php?rid=5657232&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07984.x Discussion identified future trends in the field.© 2012 Blackwell Publishing Ltd (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5657232 Thu, 02 Feb 2012 05:00:00 +0100 5657232 http://www.medworm.com/index.php?rid=5657231&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07988.x AbstractWhen Trypanosoma brucei differentiates from the bloodstream form to the procyclic form, there are decreases in the levels of many mRNAs encoding proteins required for the glycolytic pathway, and the mRNA encoding the RNA Recognition Motif protein RBP10 decreases in parallel. We show that RBP10 is a cytoplasmic protein that is specific to bloodstream‐form trypanosomes, where it is essential. Depletion of RBP10 caused decreases in many bloodstream‐form‐specific mRNAs, with increases in mRNAs associated with the early stages of differentiation. The changes were similar to, but more extensive than, those caused by glucose deprivation. Conversely, forced RBP10 expression in procyclics induced a switch towards bloodstream‐form mRNA expression patterns, with concomitant growth inh... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5657231 Thu, 02 Feb 2012 05:00:00 +0100 5657231 http://www.medworm.com/index.php?rid=5657230&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07989.x ABSTRACTAlthough oxidative stress is a key aspect of innate immunity, little is known about how host‐restricted pathogens successfully repair DNA damage. Base excision repair (BER) is responsible for correcting nucleobases damaged by oxidative stress, and is essential for bloodstream infection caused by the human pathogen, Neisseria meningitidis. We have characterised meningococcal BER enzymes involved in the recognition and removal of damaged nucleobases, and incision of the DNA backbone. We demonstrate that the bi‐functional glycosylase/lyases Nth and MutM share several overlapping activities and functional redundancy. However MutM and other members of the GO system, which deal with 8‐oxoG, a common lesion of oxidative damage, are not required for survival of N. meningitidis under ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5657230 Thu, 02 Feb 2012 05:00:00 +0100 5657230 http://www.medworm.com/index.php?rid=5657229&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07992.x SummaryQuorum sensing, a bacterial cell‐cell communication process, controls biofilm formation and virulence factor production in Vibrio cholerae, a human pathogen that causes the disease cholera. The major V. cholerae autoinducer is (S)‐3‐hydroxytridecan‐4‐one (CAI‐1). A membrane bound two‐component sensor histidine kinase called CqsS detects CAI‐1, and the CqsS‐ > LuxU‐ > LuxO phosphorelay cascade transduces the information encoded in CAI‐1 into the cell. Because the CAI‐1 ligand is known and because the signaling circuit is simple, consisting of only three proteins, this system is ideal for analyzing ligand regulation of a sensor histidine kinase. Here we reconstitute the CqsS‐ > LuxU‐ > LuxO phosphorylation cascade in vitro. We find that CAI‐1 ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5657229 Thu, 02 Feb 2012 05:00:00 +0100 5657229 http://www.medworm.com/index.php?rid=5657228&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07993.x SummaryThe LysR‐type transcription factor LeuO is involved in regulation of pathogenicity determinants and stress responses in Enterobacteriaceae, and acts as antagonist of the global repressor H‐NS. Expression of the leuO gene is repressed by H‐NS, and it is upregulated in stationary phase and under amino acid starvation conditions. Here, we show that the heterodimer of the FixJ/NarL‐type transcription regulators RcsB and BglJ strongly activates expression of leuO and that RcsB‐BglJ regulates additional loci. Activation of leuO by RcsB‐BglJ is independent of the Rcs phosphorelay system. RcsB‐BglJ binds to the leuO promoter region and activates one of two leuO promoters mapped in vivo. Moreover, LeuO antagonizes activation of leuO by RcsB‐BglJ and acts as negative autoregul... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5657228 Thu, 02 Feb 2012 05:00:00 +0100 5657228 http://www.medworm.com/index.php?rid=5657227&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07995.x ABSTRACTYeast cells normally grow by budding, but under certain specific conditions they are also able to grow in hyperpolarized forms reminiscent of hyphal growth. During vegetative growth, the synthesis of the septum that physically separates yeast cells during cytokinesis depends on the correct assembly of the septin ring. Septins and actin patches are assembled at the neck, forming two concentric rings where the actin patch ring occupies the external‐most part. This specific positioning defines a plasma membrane region at the neck from which other lateral membrane compartments are excluded. In this scenario, correct assembly of the chitin ring is dependent on the anchoring of Chs3 to the septin ring through Chs4. The anchoring of Chs3 to septins through Chs4 prevents the arrival of t... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5657227 Wed, 01 Feb 2012 05:00:00 +0100 5657227 http://www.medworm.com/index.php?rid=5644296&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07986.x SummaryThe eukaryotic bZIP transcription factors are critical players in organismal response to environmental challenges. In fungi, the production of secondary metabolites (SMs) is hypothesized as one of the responses to environmental insults, e.g. attack by fungivorous insects, yet little data to support this hypothesis exists. Here we establish a mechanism of bZIP regulation of SMs through RsmA, a recently discovered YAP‐like bZIP protein. RsmA greatly increases SM production by binding to two sites in the A. nidulans AflR promoter region, a C6 transcription factor known for activating production of the carcinogenic and anti‐predation SM, sterigmatocystin (ST). Deletion of aflR in an overexpression rsmA (OE::rsmA) background not only eliminates ST production but also significantly re... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5644296 Tue, 31 Jan 2012 20:34:56 +0100 5644296 http://www.medworm.com/index.php?rid=5644297&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07978.x In this report, we describe the involvement of TatD nuclease during programmed cell death (PCD) in the human protozoan parasite Trypanosoma brucei. T. brucei TatD nuclease showed intrinsic DNase activity, was localized in the cytoplasm and translocated to the nucleus when cells were treated with inducers previously demonstrated to cause PCD in T. brucei. Overexpression of TatD nuclease resulted in elevated PCD and conversely, loss of TatD expression by RNAi conferred significant resistance to the induction of PCD in T. brucei. Co‐immunoprecipitation studies revealed that TatD nuclease interacts with endonucleaseG suggesting that these two nucleases could form a DNA degradation complex in the nucleus. Together, biochemical activity, RNAi and subcellular localization results demonstr... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5644297 Tue, 31 Jan 2012 05:00:00 +0100 5644297 http://www.medworm.com/index.php?rid=5644299&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07979.x In this study we demonstrate that SpyA is a surface‐exposed membrane protein which is anchored to the streptococcal membrane by an N‐terminal transmembrane sequence. We identified a small gene upstream of spyA, designated spyB, which encodes a peptide of 35 amino acids, and is co‐transcribed with spyA. Expression of spyBA is strongly influenced by translational coupling: mutational inactivation of spyB translation completely abolishes translation of spyA. spyB expression increases with increasing cell density and reaches its maximum at late exponential growth phase. The SpyB N‐terminus is predicted to fold into an amphipathic α‐helix, a structural motif that targets a protein to the cytoplasmic membrane. Consistent with the prediction, we found that a SpyB fusion with peptide af... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5644299 Mon, 30 Jan 2012 05:00:00 +0100 5644299 http://www.medworm.com/index.php?rid=5644298&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07965.x SummaryIn bacteria, many small regulatory RNAs (sRNAs) are induced in response to specific environmental signals or stresses and act by base‐pairing with mRNA targets to affect protein translation or mRNA stability. In Escherichia coli, the gene for the sRNA IS061/IsrA, here renamed McaS, was predicted to reside in an intergenic region between abgR, encoding a transcription regulator and ydaL, encoding a small MutS‐related protein. We show that McaS is a ∼ 95 nt transcript whose expression increases over growth, peaking in early‐to‐mid stationary phase, or when glucose is limiting. McaS uses three discrete single‐stranded regions to regulate mRNA targets involved in various aspects of biofilm formation. McaS represses csgD, the transcription regulator of curli biogenesis an... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5644298 Mon, 30 Jan 2012 05:00:00 +0100 5644298 http://www.medworm.com/index.php?rid=5644300&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07974.x This study is an exciting addition to both the bacteriophage resistance and TA fields, and suggests a greater role for TA system‐based resistance and counter‐resistance in the world's oldest predator‐prey relationship. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5644300 Sun, 29 Jan 2012 05:00:00 +0100 5644300 http://www.medworm.com/index.php?rid=5617478&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07966.x SummaryThe Sbi protein of Staphylococcus aureus comprises two IgG‐binding domains similar to those of protein A and a region that triggers the activation of complement C3. Sbi is expressed on the cell surface but its C‐terminal domain lacks motifs associated with wall or membrane anchoring of proteins in Gram‐positive bacteria. Cell‐associated Sbi fractionates with the cytoplasmic membrane and is not solubilized during protoplast formation. S. aureus expressing Sbi truncates of the C‐terminal Y domain allowed identification of residues that are required for association of Sbi with the membrane. Recombinant Sbi bound to purified cytoplasmic membrane material in vitro and to purified lipoteichoic acid. This explains how Sbi partitions with the membrane in fractionation experiment... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5617478 Wed, 18 Jan 2012 05:00:00 +0100 5617478 http://www.medworm.com/index.php?rid=5604509&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07970.x SummarySerine‐rich repeat glycoproteins (SRRPs) are important bacterial adhesins that are conserved in streptococci and staphylococci. Fimbriae‐associated protein (Fap1) from Streptococcus parasanguinis, was the first SRRP identified; it plays an important role in bacterial biofilm formation. A gene cluster encoding glycosyltransferases and accessory secretion components is required for Fap1 biogenesis. Two glycosylation‐associated proteins, Gap1 and Gap3 within the cluster, interact with each other and function in concert in Fap1 biogenesis. Here we report the new molecular events underlying contribution of the interaction to Fap1 biogenesis. The Gap1‐deficient mutant rendered Gap3 unstable and degraded in vitro and in vivo. Inactivation of a gene encoding protease ClpP reversed t... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5604509 Wed, 18 Jan 2012 05:00:00 +0100 5604509 http://www.medworm.com/index.php?rid=5604508&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07976.x SummarySmall regulatory RNA molecules have recently been recognized as important regulatory elements of developmental processes in both eukaryotes and bacteria. We here describe a striking example in Escherichia coli that can switch between a single‐cell motile lifestyle and a multi‐cellular, sessile and adhesive state that enables biofilm formation on surfaces. For this, the bacterium needs to reprogramme its gene expression, and in many E. coli and Salmonella strains the lifestyle shift relies on control cascades that inhibit flagellar expression and activate the synthesis of curli, extracellular adhesive fibres important for co‐aggregation of cells and adhesion to biotic and abiotic surfaces. By combining bioinformatics, genetic and biochemical analysis we identified three small... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5604508 Wed, 18 Jan 2012 05:00:00 +0100 5604508 http://www.medworm.com/index.php?rid=5594031&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07957.x In this study, we determine that Saccharomyces cerevisiae Not4 E3 ligase ubiquitinates Rps7A in vivo and in vitro, but not its paralogue, Rps7B. Ubiquitinated Rps7A is detectable only in 80S and polysomes, but not in free 40S fractions. A different role of the Rps7 paralogues in vivo is supported by the observation that the deletion of Rps7A but not Rps7B is sensitive to translational inhibitors and leads to an accumulation of aggregated proteins. An important accumulation of aggregated proteins that include ribosomal proteins and ribosome‐associated chaperones is also observed in cells lacking Not4. A contribution of Not4 to ribosomal function extending beyond Rps7A ubiquitination is supported by the observation that the deletion of Not4 displays a synthetic slow growth phenotype when c... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5594031 Sun, 15 Jan 2012 05:00:00 +0100 5594031 http://www.medworm.com/index.php?rid=5594032&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07955.x SummaryAggregatibacter actinomycetemcomitans establishes a tenacious biofilm that is important for periodontal disease. The tad locus encodes the components for the secretion and biogenesis of Flp pili, which are necessary for the biofilm to form. TadZ is required, but its function has been elusive. We show that tadZ genes belong to the parA/minD superfamily of genes and that TadZ from A. actinomycetemcomitans (AaTadZ) forms a polar focus in the cell independent of any other tad locus protein. Mutations indicate that regions in AaTadZ are required for polar localization and biofilm formation. We show that AaTadZ dimerizes and that all TadZ proteins are predicted to have a Walker‐like A box. However, they all lack the conserved lysine at position 6 (K6) present in the canonical Walker�... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5594032 Fri, 13 Jan 2012 05:00:00 +0100 5594032 http://www.medworm.com/index.php?rid=5594035&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07958.x SummaryThe ESX‐1 secretion system is required for pathogenicity of Mycobacterium tuberculosis (Mtb). Despite considerable research, little is known about the structural components of ESX‐1, or how these proteins are assembled into the active secretion apparatus. Here, we exploit the functionally related ESX‐1 apparatus of Mycobacterium smegmatis (Ms) to show that fluorescently tagged proteins required for ESX‐1 activity consistently localize to the cell pole, identified by time‐lapse fluoro‐microscopy as the non‐septal (old) pole. Deletions in Msesx1 prevented polar localization of tagged proteins, indicating the need for specific protein–protein interactions in polar trafficking. Remarkably, expression of the Mtbesx1 locus in Msesx1 mutants restored polar localization of t... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5594035 Wed, 11 Jan 2012 05:00:00 +0100 5594035 http://www.medworm.com/index.php?rid=5594034&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07964.x SummaryFlgN chaperone acts as a bodyguard to protect its cognate substrates, FlgK and FlgL, from proteolysis in the cytoplasm. Docking of the FlgN–FlgK complex with the FliI ATPase of the flagellar type III export apparatus is key to the protein export process. However, a ΔfliH‐fliI flhB(P28T) mutant forms some flagella even in the absence of FliH and FliI, raising the question of how FlgN promotes the export of its cognate substrates. Here, we report that the interaction of FlgN with an integral membrane export protein, FlhA, is directly involved in efficient protein export. A ΔfliH‐fliI flhB(P28T) ΔflgN mutant caused extragenic suppressor mutations in the C‐terminal domain of FlhA (FlhAC). Pull‐down assays using GST affinity chromatography showed an interaction between FlgN ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5594034 Wed, 11 Jan 2012 05:00:00 +0100 5594034 http://www.medworm.com/index.php?rid=5594033&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07960.x SummaryLysR‐type transcriptional regulators (LTTRs) compose the largest family of homologous regulators in bacteria. Considering their prevalence, it is not surprising that LTTRs control diverse metabolic functions. Arguably, the most unexpected aspect of LTTRs is the paucity of available structural information. Solubility issues are notoriously problematic, and structural studies have only recently begun to flourish. In this issue of Molecular Microbiology, Taylor et al. present the structure of AphB, a LysR‐type regulator of virulence in Vibrio cholerae. This contribution adds significantly to the group of known full‐length atomic LTTR structures, which remains small. Importantly, this report also describes an active‐form variant. Small conformational changes in the effector‐... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5594033 Wed, 11 Jan 2012 05:00:00 +0100 5594033 http://www.medworm.com/index.php?rid=5594030&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07966.x SummaryThe Sbi protein of Staphylococcus aureus comprises two IgG binding domains similar to those of protein A and a region that triggers the activation of complement C3. Sbi is expressed on the cell surface but its C‐terminal domain lacks motifs associated with wall or membrane anchoring of proteins in Gram‐positive bacteria. Cell‐associated Sbi fractionates with the cytoplasmic membrane and is not solubilised during protoplast formation. S.aureus expressing Sbi truncates of the C‐terminal Y domain allowed identification of residues that are required for association of Sbi with the membrane. Recombinant Sbi bound to purified cytoplasmic membrane material in vitro and to purified lipoteichoic acid. This explains how Sbi partitions with the membrane in fractionation experiments yet... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5594030 Tue, 10 Jan 2012 05:00:00 +0100 5594030 http://www.medworm.com/index.php?rid=5594029&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07967.x SummaryLike other transposons of the Tn3 family, Tn4430 exhibits target immunity, a process that prevents multiple insertions of the transposon into the same DNA molecule. Immunity is conferred by the terminal inverted repeats of the transposon and is specific to each element of the family, indicating that the transposase TnpA is directly involved in the process. However, the molecular mechanism whereby this protein promotes efficient transposition into permissive targets while preventing transposition into immune targets remains unknown. Here, we demonstrate that both functions of TnpA can be uncoupled from each other by isolating and characterising mutants that are proficient in transposition (T+) but impaired in immunity (I‐). The identified T+/I‐ mutations are clustered into separa... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5594029 Tue, 10 Jan 2012 05:00:00 +0100 5594029 http://www.medworm.com/index.php?rid=5594028&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07969.x SUMMARYDivIVA is a well conserved coiled‐coil protein present in most Gram positive bacteria and has been implicated in division site selection, peptidoglycan biosynthesis, and sporulation. DivIVA proteins bind lipid membranes and characteristically accumulate at curved membrane areas, i.e. the cell poles and the division site, to which they recruit various interaction partners. We have studied the role of this morphogen in the human pathogen Listeria monocytogenes and our results suggest a novel mechanism by which DivIVA contributes to cell division. Contrary to expectation a ΔdivIVA mutant exhibited a pronounced chaining phenotype rather than a defect in cell division which we attributed to reduced extracellular levels of the autolytic enzymes p60 and MurA. We demonstrate that this is... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5594028 Tue, 10 Jan 2012 05:00:00 +0100 5594028 http://www.medworm.com/index.php?rid=5594027&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07971.x SummaryWhile bacteria such as Escherichia coli and Bacillus subtilis harbor a single circular chromosome, some freshwater cyanobacteria have multiple chromosomes per cell. The detailed mechanism(s) of cyanobacterial replication remains unclear. To elucidate the replication origin (ori), form, and synchrony of the multi‐copy genome in freshwater cyanobacteria Synechococcus elongatus PCC 7942 we constructed strain S. 7942TK that can incorporate 5‐bromo‐2′‐deoxyuridine (BrdU) into genomic DNA and analyzed its de novo DNA synthesis. The uptake of BrdU was blocked under dark and resumed after transfer of the culture to light conditions. Mapping analysis of nascent DNA fragments using a next‐generation sequencer indicated that replication starts bidirectionally from a single ori, whi... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5594027 Tue, 10 Jan 2012 05:00:00 +0100 5594027 http://www.medworm.com/index.php?rid=5594026&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07975.x SummaryEnterohemorrhagic Escherichia coli O157:H7 harbors a cryptic plasmid, pOSAK1, that carries only three ORFs: mobA (involved in plasmid mobilization), ORF1, and ORF2. Predicted proteins encoded by these two ORFs were found to share a weak homology with RnlA and RnlB, respectively, a toxin‐antitoxin system encoded on the E. coli K‐12 chromosome. Here, we report that lsoA (ORF1) encodes a toxin and lsoB (ORF2) an antitoxin. In spite of the homologies, RnlB and LsoB functioned as antitoxins against only their cognate toxins and not interchangeably with each other. Interestingly, T4 phage Dmd suppressed the toxicities of both RnlA and LsoA by direct interaction, the first example of a phage with an antitoxin against multiple toxins. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5594026 Tue, 10 Jan 2012 05:00:00 +0100 5594026 http://www.medworm.com/index.php?rid=5577115&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07956.x SummaryTranscription start points in bacteria are influenced by the nature of the RNA polymerase·promoter interaction. For Escherichia coli RNA polymerase holoenzyme containing σ70, it is presumed that specific sequence in one or more of the −10, extended −10 and −35 elements of the promoter guides the RNAP to select the cognate start point. Here, we investigated the promoter driving expression of the LEE1 operon in enteropathogenic E. coli and found two promoters separated by 10 bp, LEE1 P1A (+1) and LEE1 P1B (+10) using various in vitro biochemical tools. A unique feature of P1B was the presence of multiple transcription starts from five neighbouring As at the initial transcribed region. The multiple products did not arise from stuttering synthesis. Analytical software based ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5577115 Mon, 09 Jan 2012 05:00:00 +0100 5577115 http://www.medworm.com/index.php?rid=5577114&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07952.x SummaryHere, we describe bsrG/SR4, a novel type I toxin–antitoxin system from the SPβ prophage region of the Bacillus subtilis chromosome. The 294‐nucleotide bsrG RNA encodes a 38‐amino‐acid toxin, whereas SR4 is a 180‐nucleotide antisense RNA that acts as the antitoxin. Both genes overlap by 123 nucleotides. BsrG expression increases at the onset of stationary phase. The sr4 promoter is 6‐ to 10‐fold stronger than the bsrG promoter. Deletion of sr4 stabilizes bsrG mRNA and causes cell lysis on agar plates, which is due to the BsrG peptide and not the bsrG mRNA. SR4 overexpression could compensate cell lysis caused by overexpression of bsrG. SR4 interacts with the 3′ UTR of bsrG RNA, thereby promoting its degradation. RNase III cleaves the bsrG RNA/SR4 duplex at position 1... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5577114 Mon, 09 Jan 2012 05:00:00 +0100 5577114 http://www.medworm.com/index.php?rid=5577113&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07959.x SummaryQuorum sensing is a mechanism of cell–cell communication that bacteria use to control collective behaviours including bioluminescence, biofilm formation and virulence factor production. In the Vibrio harveyi and Vibrio cholerae quorum‐sensing circuits, multiple non‐coding small regulatory RNAs called the quorum‐regulated small RNAs (Qrr sRNAs) function to establish the global quorum‐sensing gene expression pattern by modulating translation of multiple mRNAs encoding quorum‐sensing regulatory factors. Here we show that the Qrr sRNAs post‐transcriptionally activate production of the low cell density master regulator AphA through base pairing to aphA mRNA, and this is crucial for the accumulation of appropriate levels of AphA protein at low cell density. We find that the ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5577113 Mon, 09 Jan 2012 05:00:00 +0100 5577113 http://www.medworm.com/index.php?rid=5657235&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07972.x SummarySo far, it has not been possible to identify a general sequence motif for O‐glycosylation in bacteria. In this issue, Charbonneau et al. demonstrate why O‐glycosylation is mediated by a 13‐residue strand–loop–strand motif which is part of a 19‐residue imperfect repeat in the passenger domain of bacterial autotransporters. This motif provides a convenient ‘glycosylation cassette’ and raises intriguing questions about the structural regulation of the glycosylation pathway. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5657235 Thu, 05 Jan 2012 05:00:00 +0100 5657235 http://www.medworm.com/index.php?rid=5569701&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07968.x We report that BDSF is synthesized from a fatty acid synthetic intermediate, the acyl carrier protein (ACP) thioester of 3‐hydroxydodecanoic acid. This intermediate is intercepted by protein Bcam0581 and converted to cis‐2‐dodecenoyl‐ACP. Bcam0581 is annotated as a homologue of crotonase, the first enzyme of the fatty acid degradation pathway. We demonstrated Bcam0581to be a bifunctional protein that not only catalyzed dehydration of 3‐hydroxydodecanoyl‐ACP to cis‐2‐dodecenoyl‐ACP, but also cleaved the thioester bond to give the free acid. Both activities required the same set of active site residues. Although dehydratase and thioesterase activities are known activities of the crotonase superfamily, Bcam0581 is the first protein shown to have both activities (Source: Mole... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5569701 Thu, 05 Jan 2012 05:00:00 +0100 5569701 http://www.medworm.com/index.php?rid=5569700&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07972.x AbstractSo far, it has not been possible to identify a general sequence motif for O‐glycosylation in bacteria. In this issue, Charbonneau et al. demonstrate why: O‐glycosylation is mediated by a 13‐residue strand‐loop‐strand motif which is part of a 19‐residue imperfect repeat in the passenger domain of bacterial autotransporters. This motif provides a convenient “glycosylation cassette” and raises intriguing questions about the structural regulation of the glycosylation pathway. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5569700 Thu, 05 Jan 2012 05:00:00 +0100 5569700 http://www.medworm.com/index.php?rid=5569705&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07938.x SummaryThe trypanosome mitochondrial genome, kinetoplast DNA (kDNA), is a massive network of interlocked DNA rings, including several thousand minicircles and dozens of maxicircles. The unusual complexity of kDNA would indicate that numerous proteins must be involved in its condensation, replication, segregation and gene expression. During our investigation of trypanosome mitochondrial PIF1‐like helicases, we found that TbPIF8 is the smallest and most divergent. It lacks some conserved helicase domains, thus implying that unlike other mitochondrial PIF1‐like helicases, this protein may have no enzymatic activity. TbPIF8 is positioned on the distal face of kDNA disk and its localization patterns vary with different kDNA replication stages. Stem‐loop RNAi of TbPIF8 arrests cell growth ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5569705 Wed, 04 Jan 2012 05:00:00 +0100 5569705 http://www.medworm.com/index.php?rid=5569704&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07949.x SummaryNitrogen‐fixing heterocysts are arranged in a periodic pattern on filaments of the cyanobacterium Anabaena sp. strain PCC 7120 under conditions of limiting combined nitrogen. Patterning requires two inhibitors of heterocyst differentiation, PatS and HetN, which work at different stages of differentiation by laterally suppressing levels of an activator of differentiation, HetR, in cells adjacent to source cells. Here we show that the RGSGR sequence in the 287‐amino‐acid HetN protein, which is shared by PatS, is critical for patterning. Conservative substitutions in any of the five amino acids lowered the extent to which HetN inhibited differentiation when overproduced and altered the pattern of heterocysts in filaments with an otherwise wild‐type genetic background. Conversel... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5569704 Wed, 04 Jan 2012 05:00:00 +0100 5569704 http://www.medworm.com/index.php?rid=5569703&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07946.x SummaryThe fungal cell wall, a conserved and highly dynamic structure, is essential for virulence and viability of fungal pathogens and is an important antifungal drug target. The cell wall integrity (CWI) signalling pathway regulates shape and biosynthesis of the cell wall. In this work we identified, localized and functionally characterized four putative CWI stress sensors of Aspergillus fumigatus, an airborne opportunistic human pathogen and the cause of invasive aspergillosis. We show that Wsc1 is specifically required for resistance to echinocandin antifungals. MidA is specifically required for elevated temperature tolerance and resistance to the cell wall perturbing agents congo red and calcofluor white. Wsc1, Wsc3 and MidA additionally have overlapping functions and are redundantly ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5569703 Wed, 04 Jan 2012 05:00:00 +0100 5569703 http://www.medworm.com/index.php?rid=5604507&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07981.x SummaryCytochrome c assembly requires sulfhydryls at the CXXCH heme‐binding site on the apoprotein and also chemical reduction of the heme co‐factor. In yeast mitochondria, the cytochrome heme lyases (CCHL, CC1HL) and Cyc2p catalyze covalent heme attachment to apocytochromes c and c1. An in vivo indication that Cyc2p controls a reductive step in the heme attachment reaction is the finding that the requirement for its function can be by‐passed by exogenous reductants. Although redox titrations of Cyc2p flavin (Em = ‐290 mV) indicate that reduction of a disulfide at the CXXCH site of apocytochrome c (Em= ‐265 mV) is a thermodynamically favorable reaction, Cyc2p does not act as an apocytochrome c or c1 CXXCH disulfide reductase in vitro. In contrast, Cyc2p is able to catalyze the NA... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5604507 Sun, 01 Jan 2012 05:00:00 +0100 5604507 http://www.medworm.com/index.php?rid=5594025&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07980.x In this study, high‐level purification of soluble Mga was achieved, enabling the first detailed characterization of the protein. Fluorescence titrations coupled with filter‐binding assays indicate that Mga binds cognate DNA with nanomolar affinity. Gel filtration analyses, analytical ultracentrifugation, and co‐immunoprecipitation experiments demonstrate that Mga forms oligomers in solution. Moreover, the ability of the protein to oligomerize in solution was found to correlate with transcriptional activation; DNA binding appears to be necessary but insufficient for full activity. Truncation analyses reveal that the uncharacterized C‐terminal region of Mga, possessing similarity to phosphotransferase system EIIB proteins, plays a critical role in oligomerization and in vivo activity... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5594025 Sun, 01 Jan 2012 05:00:00 +0100 5594025 http://www.medworm.com/index.php?rid=5569699&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2012.07977.x SummaryExtraintestinal pathogenic Escherichia coli (ExPEC) reside in the enteric tract as a commensal reservoir, but can transition to a pathogenic state by invading normally sterile niches, establishing infection, and disseminating to invasive sites like the bloodstream. Macrophages are required for ExPEC dissemination, suggesting the pathogen has developed mechanisms to persist within professional phagocytes. Here, we report that FimX, an ExPEC‐associated DNA invertase that regulates the major virulence factor type 1 pili (T1P), is also an epigenetic regulator of a LuxR‐like response regulator HyxR. FimX regulated hyxR expression through bidirectional phase inversion of its promoter region at sites different from the type 1 pili promoter and independent of integration host factor IHF... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5569699 Sun, 01 Jan 2012 05:00:00 +0100 5569699 http://www.medworm.com/index.php?rid=5550281&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07963.x SummaryThe gtaI gene of Rhodobacter capsulatus encodes an N‐acyl‐homoserine lactone (acyl‐HSL) synthase. Immediately 5′ of the gtaI gene is ORF rcc00328 that encodes a potential acyl‐HSL receptor protein. A combination of genetic and biochemical approaches showed that rcc00328 (renamed gtaR) modulates the production of a genetic exchange element called the gene transfer agent (RcGTA), and regulates the transcription of gtaI. Although gtaI mutants exhibited decreased levels of RcGTA production, mutagenesis of gtaR did not, whereas a gtaR/gtaI double mutant produced wild type levels of RcGTA. Because mutagenesis of gtaR suppressed the effect of the gtaI mutation, we suggest that the GtaR protein is a negative transcriptional regulator of RcGTA gene expression. We discovered that th... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5550281 Thu, 29 Dec 2011 22:09:23 +0100 5550281 http://www.medworm.com/index.php?rid=5550286&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07945.x SummaryRenewed interest in gene amplification stems from its importance in evolution and a variety of medical problems ranging from drug resistance to cancer. However, amplified DNA segments (amplicons) are not fully characterized in any organism. Here we report a novel Acinetobacter baylyi system for genome‐wide studies. Amplification mutants that consume aromatic compounds were selected under conditions requiring high‐level expression from three promoters in a linked set of chromosomal genes. Tools were developed to relocate these catabolic genes to any non‐essential chromosomal position, and 49 amplification mutants from five genomic contexts were characterized. Amplicon size (18–271 kb) and copy number (2–105) indicated that 30% of mutants carried more than 1 Mb of amplif... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5550286 Thu, 29 Dec 2011 05:00:00 +0100 5550286 http://www.medworm.com/index.php?rid=5569702&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07953.x SummaryThe Bacillus subtilis extracytoplasmic function (ECF) σ factor σM is inducible by, and confers resistance to, several cell envelope‐acting antibiotics. Here, we demonstrate that σM is responsible for intrinsic β‐lactam resistance, with σX playing a secondary role. Activation of σM upregulates several cell wall biosynthetic enzymes including one, PBP1, shown here to be a target for the beta‐lactam cefuroxime. However, σM still plays a major role in cefuroxime resistance even in cells lacking PBP1. To better define the role of σM in β‐lactam resistance, we characterized suppressor mutations that restore cefuroxime resistance to a sigM null mutant. The most frequent suppressors inactivated gdpP (yybT) which encodes a cyclic‐di‐AMP phosphodiesterase (PDE). Intriguin... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5569702 Wed, 28 Dec 2011 05:00:00 +0100 5569702 http://www.medworm.com/index.php?rid=5550285&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07953.x SummaryThe Bacillus subtilis extracytoplasmic function (ECF) σ factor σM is inducible by, and confers resistance to, several cell envelope acting antibiotics. Here, we demonstrate that σM is responsible for intrinsic β‐lactam resistance, with σX playing a secondary role. Activation of σM upregulates several cell wall biosynthetic enzymes including one, PBP1, shown here to be a target for the beta‐lactam cefuroxime. However, σM still plays a major role in cefuroxime resistance even in cells lacking PBP1. To better define the role of σM in β‐lactam resistance we characterized suppressor mutations that restore cefuroxime resistance to a sigM null mutant. The most frequent suppressors inactivated gdpP (yybT) which encodes a cyclic‐di‐AMP phosphodiesterase (PDE). Intriguingly... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5550285 Wed, 28 Dec 2011 05:00:00 +0100 5550285 http://www.medworm.com/index.php?rid=5550284&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07954.x SummaryThe tad (tight adherence) locus encodes a protein translocation system that produces a novel variant of type IV pili. The pilus assembly protein TadZ (called CpaE in Caulobacter crescentus) is ubiquitous in tad loci, but is absent in other type IV pilus biogenesis systems. The crystal structure of TadZ from E. rectale (ErTadZ), in complex with ATP and Mg2+, was determined to 2.1 Å resolution. ErTadZ contains an atypical ATPase domain with a variant of a deviant Walker‐A motif that retains ATP binding capacity while displaying only low intrinsic ATPase activity. The bound ATP plays an important role in dimerization of ErTadZ. The N‐terminal atypical receiver domain resembles the canonical receiver domain of response regulators, but has a degenerate, stripped‐down “active sit... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5550284 Wed, 28 Dec 2011 05:00:00 +0100 5550284 http://www.medworm.com/index.php?rid=5550283&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07961.x This study shows that Lag1 family proteins are generally required for polarized growth in hemiascomycetous yeast. However, in contrast to S. cerevisiae where these proteins are functionally redundant, C. albicans Lag1p (CaLag1p) and Lac1p (CaLac1p) are functionally distinct. Lack of CaLag1p, but not CaLac1p, caused severe defects in the growth and hyphal morphogenesis of C. albicans. Deletion of CaLAG1 decreased expression of the hypha‐specific HWP1 and ECE1 genes. Moreover, overexpression of CaLAG1 induced pseudohyphal growth in this organism under non‐hypha‐inducing conditions, suggesting that CaLag1p is necessary for relaying signals to induce hypha‐specific gene expression. Analysis of ceramide and sphingolipid composition revealed that CaLag1p predominantly synthesizes ceramid... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5550283 Wed, 28 Dec 2011 05:00:00 +0100 5550283 http://www.medworm.com/index.php?rid=5550282&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07962.x AbstractEukaryotic‐like serine/threonine‐kinases (STPKs) are involved in the regulation of a variety of physiological processes in bacteria. In Streptococcus pneumoniae, deletion of the single STPK gene stkP results in an aberrant cell morphology suggesting that StkP participates in pneumococcus cell division. To understand the function of StkP, we have engineered various pneumococcus strains expressing truncated or kinase‐dead forms of StkP. We show that StkP kinase activity, but also its extracellular and cytoplasmic domains per se, are required for pneumococcus cell division. Indeed, we observe that mutant cells show round or elongated shapes with non‐functional septa and a chain phenotype, delocalized sites of peptidoglycan synthesis and diffused membrane StkP localization. To ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5550282 Wed, 28 Dec 2011 05:00:00 +0100 5550282 http://www.medworm.com/index.php?rid=5534256&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07910.x SummaryHelicobacter pylori infection is an aetiological cause of gastric disorders worldwide. H. pylori has been shown to assimilate and convert host cholesterol into cholesteryl glucosides (CGs) by cholesterol‐α‐glucosyltransferase encoded by capJ. Here, we show that CapJ‐deficient (ΔcapJ) H. pylori resulted in greatly reduced type IV secretion system (TFSS)‐associated activities, including the hummingbird phenotype of AGS cells, IL‐8 production, CagA translocation/phosphorylation and CagA‐mediated signalling events. Complementation of the ΔcapJ mutation with wild type cagJ or by adding CGs‐containing lysates or exogenous fluorophore‐tagged CGs reversed the mutant phenotypes. We also show that the wild‐type but not ΔcapJ H. pylori recruited raft‐associated co... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5534256 Fri, 23 Dec 2011 15:05:42 +0100 5534256 http://www.medworm.com/index.php?rid=5534252&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07948.x This study provides new understanding of the mechanism of the assembly of a multi‐protein, multi‐lamellar structure. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5534252 Thu, 22 Dec 2011 05:00:00 +0100 5534252 http://www.medworm.com/index.php?rid=5534254&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07940.x SummaryThe superfamily of PII proteins contains the most widely distributed signalling proteins in nature. Remarkable is the variety of targets whose activity is affected by protein–protein interactions. Here we identified as novel partner for interaction with GlnK an Rnf complex, known to couple the energy of ion transport to reduce ferredoxins. The endophytic diazotrophic betaproteobacterium Azoarcus sp. strain BH72 harbours two rnf‐like clusters in the genome, of which only the rnf1 cluster was induced under conditions of N2 fixation under control of the transcriptional activator NifA. Rapid inactivation (‘DraT‐independent switch off’) of nitrogenase activity upon ammonium upshift was dependent on the Rnf1 complex. Membrane sequestration of GlnK in steady‐state N‐surplus c... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5534254 Wed, 21 Dec 2011 05:00:00 +0100 5534254 http://www.medworm.com/index.php?rid=5534253&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07944.x SummaryMyxococcus xanthus is a Gram‐negative bacterium that differentiates into environmentally resistant spores. Spore differentiation involves septation‐independent remodelling of the rod‐shaped vegetative cell into a spherical spore and deposition of a thick and compact spore coat outside of the outer membrane. Our analyses suggest that spore coat polysaccharides are exported to the cell surface by the Exo outer membrane polysaccharide export/polysaccharide co‐polymerase 2a (OPX/PCP‐2a) machinery. Conversion of the capsule‐like polysaccharide layer into a compact spore coat layer requires the Nfs proteins which likely form a complex in the cell envelope. Mutants in either nfs, exo or two other genetic loci encoding homologues of polysaccharide synthesis enzymes fail to compl... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5534253 Wed, 21 Dec 2011 05:00:00 +0100 5534253 http://www.medworm.com/index.php?rid=5520940&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07941.x This study tested the ability of all yeast bHLH proteins to regulate PHO5 expression and identified inositol‐mediated regulation via the Ino2p/Ino4p bHLH proteins. Ino2p/Ino4p are known regulators of phospholipid biosynthetic genes. Genetic epistasis experiments showed that regulation by inositol required a third UAS site (UASp3 at −194). ChIP assays showed that Ino2p:Ino4p bind the PHO5 promoter and that this binding is dependent on Pho4p binding. These results demonstrate that phospholipid biosynthesis is co‐ordinated with phosphate utilization via the bHLH proteins. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5520940 Mon, 19 Dec 2011 05:00:00 +0100 5520940 http://www.medworm.com/index.php?rid=5512991&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07937.x In conclusion, we show that c3 is not an essential chromosomal element, rather a large plasmid that encodes virulence, secondary metabolism and other accessory functions in Bcc bacteria. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5512991 Fri, 16 Dec 2011 05:00:00 +0100 5512991 http://www.medworm.com/index.php?rid=5512994&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07931.x SummaryBacteriophages recognize and bind specific receptors to infect suitable hosts. Bacteriophage SPP1 targets at least two receptors of the Bacillus subtilis cell envelope, the glucosylated wall teichoic acids and the membrane protein YueB. Here, we identify a key virion protein for YueB binding and for the trigger of DNA ejection. Extracts from B. subtilis‐infected cells applied to a YueB affinity matrix led to preferential capturing of gp21 from SPP1. To assess the significance of this interaction, we isolated mutant phages specifically affected in YueB binding. The mutants exhibited a very low inactivation rate and a strong defect to eject DNA when challenged with YueB. The phenotype correlated with presence of a single amino acid substitution in the gp21 carboxyl terminus, defin... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5512994 Thu, 15 Dec 2011 05:00:00 +0100 5512994 http://www.medworm.com/index.php?rid=5512993&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07935.x SummaryMutants of the fungus Ustilago maydis defective in the RecQ helicase Blm are highly sensitive to killing by the DNA replication stressor hydroxyurea. This sensitivity or toxicity is dependent on the homologous recombination (HR) system and apparently results from formation of dead‐end HR DNA intermediates. HU toxicity can be suppressed by deletion of the gene encoding Brh2, the BRCA2 orthologue that serves to regulate HR by mediating Rad51 filament formation on single‐stranded DNA. Brh2 harbours two different DNA‐binding domains that contribute to HR function. DNA‐binding activity from a single domain is sufficient to provide Brh2 functional activity in HR, but to enable HU‐induced killing two functional DNA‐binding domains must be present. Despite this stringent require... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5512993 Thu, 15 Dec 2011 05:00:00 +0100 5512993 http://www.medworm.com/index.php?rid=5512992&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07936.x In this study we use a library of 41 spore coat proteins fused to the green fluorescent protein to examine spore coat morphogenesis over the time‐course of sporulation. We found considerable diversity in the localization dynamics of coat proteins and were able to establish six classes based on localization kinetics. Localization dynamics correlate well with the known transcriptional regulators of coat gene expression. Previously, we described the existence of multiple layers in the mature spore coat. Here, we find that the spore coat initially assembles a scaffold that is organized into multiple layers on one pole of the spore. The coat then encases the spore in multiple co‐ordinated waves. Encasement is driven, at least partially, by transcription of coat genes and deletion of sporula... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5512992 Thu, 15 Dec 2011 05:00:00 +0100 5512992 http://www.medworm.com/index.php?rid=5512990&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07947.x In this study, we show that AQ production is modulated by an orphan P. aeruginosa sensor kinase. Transcriptional studies of the sensor kinase (MxtR) mutant demonstrated that an induced expression of MexT, a LysR‐type transcriptional regulator, largely determined the global transcriptional profile. Thereby, over‐expression of the MexT regulated MexEF‐OprN efflux pump, led to a delayed expression of the AQ biosynthetic genes and of AQ dependent virulence factors. Furthermore, we demonstrated that autophosphorylation of MxtR was inhibited by ubiquinone, the central electron carrier of respiration in in vitro experiments. Our results elucidate on a mechanism by which P. aeruginosa senses environmental conditions and adapts by controlling the production of interbacterial AQ signal molecul... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5512990 Wed, 14 Dec 2011 05:00:00 +0100 5512990 http://www.medworm.com/index.php?rid=5512989&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07950.x In this study, a regulatory subunit of cAMP‐dependent protein kinase (Ldpkar1), homologous to mammalian class I cAMP‐dependent protein kinase regulatory subunit, has been identified from L. donovani. Further characterization suggested possible interaction of LdPKAR1 with PKA catalytic subunits and inhibition of PKA activity. This PKA regulatory subunit is expressed in all lifecycle stages and its expression attained maximum level in stationary phase promastigotes, which are biochemically similar to the infective metacyclic promastigotes. Starvation condition, the trigger for metacyclogenesis in the parasite, elevates LdPKAR1 expression and under starvation condition promastigotes overexpressing Ldpkar1 attained metacyclic features earlier than normal cells. Furthermore, Ldpkar1 over ex... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5512989 Wed, 14 Dec 2011 05:00:00 +0100 5512989 http://www.medworm.com/index.php?rid=5501738&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07932.x SummaryThe etiological agent of Lyme disease, Borrelia burgdorferi, is transmitted by ticks of the Ixodes genus and, if untreated, can cause significant morbidity in affected individuals. Recent reports have shown that polyunsaturated fatty acids in the B. burgdorferi cell envelope are potential targets for oxidative damage, which can be lethal. How B. burgdorferi responds to this assault is not known. Herein we report evidence that bb0646 codes for a lipase that is located within the bosR operon and that has specificity for both saturated and polyunsaturated fatty acids. Specifically, strains harbouring mutated copies of the lipase, either in the form of an insertionally inactivated construct or site‐directed mutations within the active site, demonstrated attenuated lipolytic and ha... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5501738 Sun, 11 Dec 2011 05:00:00 +0100 5501738 http://www.medworm.com/index.php?rid=5501737&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07930.x SummaryBacterial conjugation is important for the acquisition of virulence and antibiotic resistance genes. We investigated the mechanism of conjugation in Gram‐positive pathogens using a model plasmid pCW3 from Clostridium perfringens. pCW3 encodes tetracycline resistance and contains the tcp locus, which is essential for conjugation. We showed that the unique TcpC protein (359 amino acids, 41 kDa) was required for efficient conjugative transfer, localized to the cell membrane independently of other conjugation proteins, and that membrane localization was important for its function, oligomerization and interaction with the conjugation proteins TcpA, TcpH and TcpG. The crystal structure of the C‐terminal component of TcpC (TcpC99–359) was determined to 1.8‐Å resolution. TcpC99�... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5501737 Sun, 11 Dec 2011 05:00:00 +0100 5501737 http://www.medworm.com/index.php?rid=5501736&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07933.x SummaryGlutathione (γ‐glutamylcysteinyl‐glycine, GSH) has vital functions as thiol redox buffer and cofactor of antioxidant and detoxification enzymes. Plasmodium falciparum possesses a functional GSH biosynthesis pathway and contains mM concentrations of the tripeptide. It was impossible to delete in P. falciparum the genes encoding γ‐glutamylcysteine synthetase (γGCS) or glutathione synthetase (GS), the two enzymes synthesizing GSH, although both gene loci were not refractory to recombination. Our data show that the parasites cannot compensate for the loss of GSH biosynthesis via GSH uptake. This suggests an important if not essential function of GSH biosynthesis pathway for the parasites. Treatment with the irreversible inhibitor of γGCS L‐buthionine sulfoximine (BSO) redu... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5501736 Sun, 11 Dec 2011 05:00:00 +0100 5501736 http://www.medworm.com/index.php?rid=5501735&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07934.x SummaryBacterial flagellar motors are intricate nanomachines in which the stator units and rotor component FliM may be dynamically exchanged during function. Similar to other bacterial species, the gammaproteobacterium Shewanella putrefaciens CN‐32 possesses a complete secondary flagellar system along with a corresponding stator unit. Expression of the secondary system occurs during planktonic growth in complex media and leads to the formation of a subpopulation with one or more additional flagella at random positions in addition to the primary polar system. We used physiological and phenotypic characterizations of defined mutants in concert with fluorescent microscopy on labelled components of the two different systems, the stator proteins PomB and MotB, the rotor components FliM1 and F... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5501735 Sun, 11 Dec 2011 05:00:00 +0100 5501735 http://www.medworm.com/index.php?rid=5483931&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07925.x SummaryClostridium perfringens possesses at least two functional quorum sensing (QS) systems, i.e. an Agr‐like system and a LuxS‐dependent AI‐2 system. Both of those QS systems can reportedly control in vitro toxin production by C. perfringens but their importance for virulence has not been evaluated. Therefore, the current study assessed whether these QS systems might regulate the pathogenicity of CN3685, a C. perfringens type C strain. Since type C isolates cause both haemorrhagic necrotic enteritis and fatal enterotoxemias (where toxins produced in the intestines are absorbed into the circulation to target other internal organs), the ability of isogenic agrB or luxS mutants to cause necrotizing enteritis in rabbit small intestinal loops or enterotoxemic lethality in mice was e... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5483931 Wed, 07 Dec 2011 05:00:00 +0100 5483931 http://www.medworm.com/index.php?rid=5550287&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07943.x SummaryPolyadenylation is a universal post‐transcriptional modification involved in degradation and quality control of bacterial RNAs. In Escherichia coli, it is admitted that any accessible RNA 3′ end can be tagged by a poly(A) tail for decay. However, we do not have yet an overall view of the population of polyadenylated molecules. The sampling of polyadenylated RNAs presented here demonstrates that rRNA fragments and tRNA precursors originating from the internal spacer regions of the rrn operons, in particular, rrnB are abundant poly(A) polymerase targets. Focused analysis showed that Glu tRNA precursors originating from the rrnB and rrnG transcripts exhibit long 3′ trailers that are primarily removed by PNPase and to a lesser extent by RNase II and poly(A) polymerase. Moreover, 3... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5550287 Tue, 06 Dec 2011 05:00:00 +0100 5550287 http://www.medworm.com/index.php?rid=5534255&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07942.x SummaryBloodstream infection with Staphylococcus aureus is common and can be fatal. However, virulence factors that contribute to lethality in S. aureus bloodstream infection are poorly defined. We discovered that LukED, a commonly overlooked leucotoxin, is critical for S. aureus bloodstream infection in mice. We also determined that LukED promotes S. aureus replication in vivo by directly killing phagocytes recruited to sites of haematogenously seeded tissue. Furthermore, we established that murine neutrophils are the primary target of LukED, as the greater virulence of wild‐type S. aureus compared with a lukED mutant was abrogated by depleting neutrophils. The in vivo toxicity of LukED towards murine phagocytes is unique among S. aureus leucotoxins, implying its crucial role ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5534255 Tue, 06 Dec 2011 05:00:00 +0100 5534255 http://www.medworm.com/index.php?rid=5483929&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07942.x SUMMARYBloodstream infection with Staphylococcus aureus is common and can be fatal. However, virulence factors that contribute to lethality in S. aureus bloodstream infection are poorly defined. We discovered that LukED, a commonly overlooked leukotoxin, is critical for S. aureus bloodstream infection in mice. We also determined that LukED promotes S. aureus replication in vivo by directly killing phagocytes recruited to sites of hematogenously‐seeded tissue. Furthermore, we established that murine neutrophils are the primary target of LukED, as the greater virulence of wild type S. aureus compared to a lukED mutant was abrogated by depleting neutrophils. The in vivo toxicity of LukED toward murine phagocytes is unique among S. aureus leukotoxins, implying its crucial role in pathogenesi... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5483929 Tue, 06 Dec 2011 05:00:00 +0100 5483929 http://www.medworm.com/index.php?rid=5483928&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07939.x ABSTRACTRNA‐dependent RNA polymerases (RdRPs) play key roles in the RNA silencing pathway in a number of organisms. They have been involved in the production of double stranded RNA (dsRNA) molecules that initiate the silencing mechanism as well as in the amplification of the silencing signal. The roles of RdRPs from fungi in these processes are poorly described compared to other eukaryotes. RNA silencing in the zygomycete Mucor circinelloides exhibits uncommon features, such as induction by self‐replicative sense transgenes and an amplification process associated with two size classes of antisense small interfering RNAs (siRNAs). To investigate the function of fungal RdRP proteins in initiation and amplification of silencing we have cloned and characterized two different rdrp genes in ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5483928 Tue, 06 Dec 2011 05:00:00 +0100 5483928 http://www.medworm.com/index.php?rid=5512988&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07951.x AbstractKinesins are motor‐based transport proteins that play diverse roles in various cellular processes. The trypanosome genome lacks the homologs of many conserved mitotic kinesins, but encodes a number of trypanosome‐specific kinesins with unknown function. Here, we report the biochemical and functional characterization of TbKIN‐C, a trypanosome‐specific kinesin, which was initially identified through an RNAi screen for cytokinesis genes in T. brucei. TbKIN‐C possesses in vitro ATPase activity and associates with cytoskeletal tubulin microtubules in vivo. It is distributed throughout the cytoskeleton with a focal enrichment at the posterior end of the cell during early cell cycle stages. RNAi of TbKIN‐C resulted in distorted cell shape with an elongated posterior filled wit... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5512988 Thu, 01 Dec 2011 05:00:00 +0100 5512988 http://www.medworm.com/index.php?rid=5493025&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07866.x SummaryThe mechanism by which prokaryotic cells organize and segregate their intracellular organelles during cell division has recently been the subject of substantial interest. Unlike other microorganisms, magnetotactic bacteria (MTB) form internal magnets (known as magnetosome chain) for magnetic orientation, and thus face an additional challenge of dividing and equipartitioning this magnetic receptor to their daughter cells. Although MTB have been investigated more than four decades, it is only recently that the basic mechanism of how MTB divide and segregate their magnetic organelles has been addressed. In this issue of Molecular Microbiology, the cell cycle of the model magnetotactic bacterium, Magnetospirillum gryphiswaldense is characterized by Katzmann and co‐workers. The authors... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5493025 Thu, 01 Dec 2011 05:00:00 +0100 5493025 http://www.medworm.com/index.php?rid=5483927&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07943.x SummaryPolyadenylation is a universal post‐transcriptional modification involved in degradation and quality control of bacterial RNAs. In E. coli, it is admitted that any accessible RNA 3′ end can be tagged by a poly(A) tail for decay. However, we do not have yet an overall view of the population of polyadenylated molecules. The sampling of polyadenylated RNAs presented here demonstrates that rRNA fragments and tRNA precursors originating from the internal spacer regions of the rrn operons, in particular rrnB, are abundant poly(A) polymerase targets. Focused analysis showed that Glu tRNA precursors originating from the rrnB and rrnG transcripts exhibit long 3’ trailers that are primarily removed by PNPase and to a lesser extent by RNase II and poly(A) polymerase. Moreover 3’ trimmi... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5483927 Thu, 01 Dec 2011 05:00:00 +0100 5483927 http://www.medworm.com/index.php?rid=5465772&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07922.x SummaryBacterial L‐forms are cell wall‐less forms of bacteria that usually grow with a conventional cell wall. Despite being important for research, L‐forms are difficult to generate reproducibly and research in this area is challenging. The manuscript published in this issue by Domínguez‐Cuevas and colleagues reports a method to rapidly, quantitatively and reproducibly generate populations of L‐forms in Bacillus subtilis. Importantly, the methodology may be applicable to other bacteria heralding a new era of L‐form research. Moreover, the genetic requirements of this method provide insights into how Lipid II synthesis and autolysin expression/activity are normally balanced and the central role of the WalRK two‐component system in this process. (Source: Molecular Microbiolog... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5465772 Tue, 29 Nov 2011 05:00:00 +0100 5465772 http://www.medworm.com/index.php?rid=5454452&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07920.x SummaryL‐forms are variants of common bacteria that can grow and proliferate without a cell wall. Little is known about their molecular cell biology but they undergo a remarkable mode of proliferation that is independent of the normally essential FtsZ‐dependent division machinery. We have isolated a strain of Bacillus subtilis that can quickly and quantitatively convert from the walled to the L‐form state. Analysis of the transition process identified an unexpected ‘escape’ step needed for L‐form emergence from the rod. Mutations in two different genes, walR and sepF, contribute to the high frequency of escape: walR, a transcriptional regulator involved in cell wall homeostasis; and sepF, required for accurate and efficient cell division. Time‐lapse imaging shows that the mut... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5454452 Tue, 29 Nov 2011 05:00:00 +0100 5454452 http://www.medworm.com/index.php?rid=5447955&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07929.x SUMMARYSpore formation in Bacillus subtilis takes place in a sporangium consisting of two chambers, the forespore and the mother cell, which are linked by pathways of cell‐cell communication. One pathway, which couples the proteolytic activation of the mother cell transcription factor σE to the action of a forespore synthesized signal molecule, SpoIIR, has remained enigmatic. Signalling by SpoIIR requires the protein to be exported to the intermembrane space between forespore and mother cell, where it will interact with and activate the integral membrane protease SpoIIGA. Here we show that SpoIIR signal activity as well as the cleavage of its N‐terminal extension is strictly dependent on the prespore fatty acid biosynthetic machinery. We also report that a conserved threonine residue ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5447955 Sat, 26 Nov 2011 15:38:15 +0100 5447955 http://www.medworm.com/index.php?rid=5483930&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07929.x SummarySpore formation in Bacillus subtilis takes place in a sporangium consisting of two chambers, the forespore and the mother cell, which are linked by pathways of cell–cell communication. One pathway, which couples the proteolytic activation of the mother cell transcription factor σE to the action of a forespore synthesized signal molecule, SpoIIR, has remained enigmatic. Signalling by SpoIIR requires the protein to be exported to the intermembrane space between forespore and mother cell, where it will interact with and activate the integral membrane protease SpoIIGA. Here we show that SpoIIR signal activity as well as the cleavage of its N‐terminal extension is strictly dependent on the prespore fatty acid biosynthetic machinery. We also report that a conserved threonine residue ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5483930 Wed, 23 Nov 2011 05:00:00 +0100 5483930 http://www.medworm.com/index.php?rid=5465773&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07921.x SummaryThe φCh1 myovirus, which infects the haloalkaliphilic archaeon Natrialba magadii, contains an invertible region that comprises the convergent open reading frames (ORFs) 34 and 36, which code for the putative tail fibre proteins gp34 and gp36 respectively. The inversion leads to an exchange of the C‐termini of these proteins, thereby creating different types of tail fibres. Gene expression experiments revealed that only ORF34 is transcribed, indicating that φCh1 produces tail fibre proteins exclusively from this particular ORF. Only one of the two types of tail fibres encoded by ORF34 is able to bind to Nab. magadii in vitro. This is reflected by the observation that during the early phases of the infection cycle, the lysogenic strain L11 carries its invertible region exclusive... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5465773 Wed, 23 Nov 2011 05:00:00 +0100 5465773 http://www.medworm.com/index.php?rid=5447961&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07921.x AbstractThe φCh1 myovirus, which infects the haloalkaliphilic archaeon Natrialba magadii, contains an invertible region that comprises the convergent open reading frames (ORFs) 34 and 36, which code for the putative tail fiber proteins gp34 and gp36, respectively. The inversion leads to an exchange of the C‐termini of these proteins, thereby creating different types of tail fibers. Gene expression experiments revealed that only ORF34 is transcribed, indicating that φCh1 produces tail fiber proteins exclusively from this particular ORF. Only one of the 2 types of tail fibers encoded by ORF34 is able to bind to Nab. magadii in vitro. This is reflected by the observation that during the early phases of the infection cycle, the lysogenic strain L11 carries its invertible region exclusively... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5447961 Wed, 23 Nov 2011 05:00:00 +0100 5447961 http://www.medworm.com/index.php?rid=5447960&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07923.x In this study we identify FtsA mutants impaired for self‐interaction. Such mutants are able to support Z‐ring assembly and are also able to bypass the requirement for ZipA. These mutants, including FtsA*, have reduced ability to self‐interact but interact normally with FtsZ and are less toxic if overexpressed. These results do not support a model in which FtsA monomers antagonize FtsZ polymers. Instead, we propose a new model in which FtsA self‐interaction competes with its ability to recruit downstream proteins. In this model FtsA self‐interaction at the Z ring is antagonized by ZipA, allowing unpolymerized FtsA to recruit downstream proteins such as FtsN. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5447960 Wed, 23 Nov 2011 05:00:00 +0100 5447960 http://www.medworm.com/index.php?rid=5447959&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07924.x AbstractFliT is a flagellar type III export chaperone specific for the filament‐capping protein FliD. The FliT/FliD complex binds to the FliI ATPase of the flagellar export apparatus. The C‐terminal α4 helix of FliT controls its interaction with FliI but it remains unknown how it does so. Here, we analyzed the FliI‐FliT interaction by pull‐down assays using GST affinity chromatography. FliT94, missing the C‐terminal α4 helix, bound to the extreme N‐terminal region of FliI (FliIEN) with high affinity and to the C‐terminal ATPase domain (FliICAT) with low affinity. The C‐terminal α4 helix of FliT suppressed the interaction with FliIEN. FliH and FliT94 bound to a common binding site on FliIEN and hence FliH induced the release of FliI from FliT94 in an ATP‐independent man... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5447959 Wed, 23 Nov 2011 05:00:00 +0100 5447959 http://www.medworm.com/index.php?rid=5447958&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07926.x This study explores the genetic, structural and functional differences of amylovoran and stewartan, and their potential role in host adaptation. We report that the pyruvyl transferase gene in P. stewartii is non‐functional, while the terminal glucosyl transferase is catalytically active. Conversely, in E. amylovora, the homologous glucosyl tranferase activity appears to be relatively ineffective, while the pyruvyl transferase function predominates. We also show that the pyruvylated vs. glucosylated EPS require specific repeating unit translocases (Wzx). We discuss the evolutionary, functional and biological implications of the pyruvylated and glucosylated polymers and their potential contribution to plant and insect host adaptation. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5447958 Wed, 23 Nov 2011 05:00:00 +0100 5447958 http://www.medworm.com/index.php?rid=5447957&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07927.x This study has identified horizontally‐acquired genomic regions of enterohaemorrhagic Escherichia coli O157:H7 that regulate expression of the type III secretion (T3S) system encoded by the locus of enterocyte effacement (LEE). Deletion of O‐island 51, a 14.93 kb cryptic prophage (CP‐933C), resulted in a reduction in LEE expression and T3S. The deletion also had a reduced capacity to attach to epithelial cells and significantly reduced E. coli O157 excretion levels from sheep. Further characterisation of O‐island 51 identified a novel positive regulator of the LEE, encoded by ecs1581 in the E. coli O157:H7 strain Sakai genome and present but not annotated in the E. coli strain EDL933 sequence. Functionally important residues of ECs1581 were identified based on phenotypic variants p... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5447957 Wed, 23 Nov 2011 05:00:00 +0100 5447957 http://www.medworm.com/index.php?rid=5447956&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07928.x SummaryChemoreceptors transmit signals from the environment to the flagellar motors via a histidine kinase that controls the phosphorylation level of the effector protein CheY. The cytoplasmic domain of chemoreceptors is strongly conserved and consists of a long alpha‐helical hairpin that forms, in the dimer, a coiled‐coil four‐helix bundle. Changes in this domain during evolution are characterized by the presence of seven‐residue insertions/deletions located symmetrically with respect to the hairpin turn, suggesting that specific interactions between the helices that form the hairpin are required for function. We assessed the impact of seven‐residue deletions on the signaling ability and higher‐order organization of the serine chemoreceptor from Escherichia coli. Our results i... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5447956 Wed, 23 Nov 2011 05:00:00 +0100 5447956 http://www.medworm.com/index.php?rid=5437719&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07915.x SummaryBacterial lipoproteins play a crucial role in virulence in some Gram‐positive bacteria. However, the role of lipoprotein biosynthesis in Bacillus anthracis is unknown. We created a B. anthracis mutant strain altered in lipoproteins by deleting the lgt gene encoding the enzyme prolipoprotein diacylglyceryl transferase, which attaches the lipid anchor to prolipoproteins. 14C‐palmitate labelling confirmed that the mutant strain lacked lipoproteins, and hydrocarbon partitioning showed it to have decreased surface hydrophobicity. The anthrax toxin proteins were secreted from the mutant strain at nearly the same levels as from the wild‐type strain. The TLR2‐dependent TNF‐α response of macrophages to heat‐killed lgt mutant bacteria was reduced. Spores of the lgt mutant germi... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5437719 Tue, 22 Nov 2011 05:00:00 +0100 5437719 http://www.medworm.com/index.php?rid=5437724&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07896.x We present the crystal structure of PulS, an all‐helical bundle that is structurally distinct from proteins with similar functions. Replacement of valine at position 42 in a charged groove of PulS abolished complex formation between a non‐lipidated variant of PulS and a peptide corresponding to the unfolded region of PulD to which PulS binds (the S‐domain), in vitro, as well as PulS function in vivo. Substitutions of other residues in the groove also diminished the interaction with the S‐domain in vitro but exerted less marked effects in vivo. We propose that the interaction between PulS and the S‐domain is maintained through a structural adaptation of the two proteins that could be influenced by cis factors such as the fatty acyl groups on PulS, as well as periplasmic trans‐ac... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5437724 Mon, 21 Nov 2011 05:00:00 +0100 5437724 http://www.medworm.com/index.php?rid=5437721&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07908.x SummaryAlthough various mutant strains of the fission yeast Schizosaccharomyces pombe exhibit non‐sexual flocculation, little is known about the mechanistic basis for this phenomenon, nor have genes encoding the implicated flocculin been identified. In the budding yeast Saccharomyces cerevisiae, the transcription factor Flo8 controls expression of some of the genes involved in non‐sexual flocculation. We have found that overexpression of S. cerevisiae FLO8 induced non‐sexual flocculation in S. pombe. This non‐sexual flocculation was Ca2+‐dependent, and was inhibited by addition of galactose, but not by mannose, glucose or sucrose. In the FLO8‐overexpressing strain, a gene designated gsf2+ (galactose‐specific flocculation) was specifically induced. The gsf2+ gene was also ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5437721 Mon, 21 Nov 2011 05:00:00 +0100 5437721 http://www.medworm.com/index.php?rid=5437720&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07911.x SummarySmall non‐coding RNA molecules (sRNA) are key regulators participating in complex networks, which adapt metabolism in response to environmental changes. In this issue of Molecular Microbiology, and in a related paper in Proc. Natl. Acad. Sci. USA, Moreno and colleagues and Sonnleitner and colleagues report on novel sRNAs, which act as decoys to inhibit the activity of the master post‐transcriptional regulatory protein Crc. Crc is a key protein involved in carbon catabolite repression that optimizes metabolism improving the adaptation of the bacteria to their diverse habitats. Crc is a novel RNA‐binding protein that regulates translation of multiple target mRNAs. Two regulatory sRNAs in Pseudomonas putida mimic the natural mRNA targets of Crc and counteract the action of Crc by... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5437720 Mon, 21 Nov 2011 05:00:00 +0100 5437720 http://www.medworm.com/index.php?rid=5428637&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07913.x SummaryAdhesion of bacterial cells to surfaces can be mediated by a wide variety of extracellular structures, which can either recognize specific molecular motifs or adhere in non‐specific ways to multiple types of surfaces. The attachment is thought to be highly regulated, but the underlying sensory mechanism(s) are poorly understood. In the α‐proteobacterium Caulobacter crescentus, the formation of adhesive organelles is ‘hardwired’ into the cell cycle regulatory circuitry. In this issue of Molecular Microbiology, Li et al. employed this model organism to examine the adhesion process and the transition from temporary to permanent attachment using total internal reflection fluorescence (TIRF) microscopy. Surprisingly, they observed that adhesin production was not only under dev... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5428637 Fri, 18 Nov 2011 05:00:00 +0100 5428637 http://www.medworm.com/index.php?rid=5418539&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07899.x SummaryUpon initiating replication of the Caulobacter chromosome, one copy of the parS centromere remains at the stalked pole; the other moves to the distal pole. We identified the segregation dynamics and compaction characteristics of newly replicated Caulobacter DNA during transport (highly variable from cell to cell) using time‐lapse fluorescence microscopy. The parS centromere and a length (also highly variable) of parS proximal DNA on each arm of the chromosome are segregated with the same relatively slow transport pattern as the parS locus. Newly replicated DNA further than about 100 kb from parS segregates with a different and faster pattern, while loci at 48 kb from parS segregate with the slow pattern in some cells and the fast pattern in others. The observed parS‐proximal... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5418539 Wed, 16 Nov 2011 05:00:00 +0100 5418539 http://www.medworm.com/index.php?rid=5404957&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07916.x AbstractThe ability to move towards favorable conditions provides fundamental advantages to organisms. Interestingly, flagella as motility structures evolved independently in the bacterial and the archaeal kingdom. Whereas bacterial flagella have been intensively studied, our knowledge regarding the archaeal counterpart is mostly restricted to Euryarchaeota rather than crenarchaeal flagella. We therefore investigated the flagellar assembly system of the crenarchaeal model organism Sulfolobus acidocaldarius in vivo.Promoter studies and qRT‐PCR analyses of the flagella gene cluster provided evidence that the expression of the fla genes was induced by tryptone starvation. Moreover, we confirmed presence of a secondary fla promoter within the flaB gene that regulates the transcription of dow... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5404957 Mon, 14 Nov 2011 05:00:00 +0100 5404957 http://www.medworm.com/index.php?rid=5404956&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07914.x SummaryFurX is a tetrameric Zn‐dependent alcohol dehydrogenase (ADH) from Cupriavidus necator JMP134. The enzyme rapidly reduces furfural with NADH as the reducing power. For the first time among characterized ADHs, the high‐resolution structures of all reaction steps were obtained in a time‐resolved manner, thereby illustrating the complete catalytic events of NADH‐dependent reduction of furfural and the dynamic Zn2+‐coordination among Glu66, water, substrate and product. In the fully closed conformation of the NADH complex, the catalytic turnover proved faster than observed for the partially closed conformation due to an effective proton transfer network. The domain motion triggered by NAD(H) association/dissociation appeared to facilitate dynamic interchanges in Zn2+‐coordin... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5404956 Mon, 14 Nov 2011 05:00:00 +0100 5404956 http://www.medworm.com/index.php?rid=5397523&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07894.x SummaryRNase E is an essential endoribonuclease with a preference for RNA substrates with 5′‐monophosphate ends. Primary transcripts, which have 5′ triphosphate ends, are thus protected from RNase E. Their conversion to 5′‐monophosphate transcripts by RppH is a prerequisite for RNase E‐mediated processing and degradation. 5′‐monophosphate recognition involves binding to a subdomain in the catalytic core of RNase E known as the 5′ sensor. There are, however, transcripts that can be attacked directly by RNase E in a 5′‐end‐independent pathway. Direct entry involves elements outside of the catalytic domain that are located in the carboxyl terminal half (CTH) of RNase E. Strains harbouring rne alleles that express variants of RNase E in which 5′ sensing (rneR169Q) or ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397523 Thu, 10 Nov 2011 05:00:00 +0100 5397523 http://www.medworm.com/index.php?rid=5397527&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07866.x SummaryThe mechanism by which prokaryotic cells organize and segregate their intracellular organelles during cell division has recently been the subject of substantial interest. Unlike other microorganisms, magnetotactic bacteria (MTB) form internal magnets (known as magnetosome chain) for magnetic orientation, and thus face an additional challenge of dividing and equipartitioning this magnetic receptor to their daughter cells. Although MTB have been investigated more than four decades, the basic mechanism of how MTB divide and segregate their magnetic organelles has remained unknown. In this issue of Molecular Microbiology, the cell cycle of the model magnetotactic bacterium, Magnetospirillum gryphiswaldense is characterized by Katzmann and co‐workers. The authors have noticed that M.�... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397527 Tue, 08 Nov 2011 05:00:00 +0100 5397527 http://www.medworm.com/index.php?rid=5397526&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07886.x SummaryCalcineurin, a heterodimer composed of the catalytic (CnaA) and regulatory (CnaB) subunits, plays key roles in growth, virulence and stress responses of fungi. To investigate the contribution of CnaA and CnaB to hyphal growth and septation, ΔcnaB and ΔcnaAΔcnaB strains of Aspergillus fumigatus were constructed. CnaA colocalizes to the contractile actin ring early during septation and remains at the centre of the mature septum. While CnaB's septal localization is CnaA‐dependent, CnaA's septal localization is CnaB‐independent, but CnaB is required for CnaA's function at the septum. Catalytic null mutations in CnaA caused stunted growth despite septal localization of the calcineurin complex, indicating the requirement of calcineurin activity at the septum. Compared to the ΔcnaA... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397526 Tue, 08 Nov 2011 05:00:00 +0100 5397526 http://www.medworm.com/index.php?rid=5397525&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07872.x SummaryBacterial conjugation is a form of type IV secretion that transports protein and DNA to recipient cells. Specific bacteriophage exploit the conjugative pili and cell envelope spanning protein machinery of these systems to invade bacterial cells. Infection by phage R17 requires F‐like pili and coupling protein TraD, which gates the cytoplasmic entrance of the secretion channel. Here we investigate the role of TraD in R17 nucleoprotein uptake and find parallels to secretion mechanisms. The relaxosome of IncFII plasmid R1 is required. A ternary complex of plasmid oriT, TraD and a novel activation domain within the N‐terminal 992 residues of TraI contributes a key mechanism involving relaxase‐associated properties of TraI, protein interaction and the TraD ATPase. Helicase‐associ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397525 Tue, 08 Nov 2011 05:00:00 +0100 5397525 http://www.medworm.com/index.php?rid=5397534&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07883.x SummaryThe C‐terminus of the NuoL subunit of Complex I includes a long amphipathic α‐helix positioned parallel to the membrane, which has been considered to function as a piston in the proton pumping machinery. Here, we have introduced three types of mutations into the nuoL gene to test the piston‐like function. First, NuoL was truncated at its C‐ and N‐termini, which resulted in low production of a fragile Complex I with negligible activity. Second, we mutated three partially conserved residues of the amphipathic α‐helix: Asp and Lys residues and a Pro were substituted for acidic, basic or neutral residues. All these variants exhibited almost a wild‐type phenotype. Third, several substitutions and insertions were made to reduce rigidity of the amphipathic α‐helix, and/o... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397534 Mon, 07 Nov 2011 05:00:00 +0100 5397534 http://www.medworm.com/index.php?rid=5397533&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07871.x SummaryCell morphology and viability in Eubacteria is dictated by the architecture of peptidoglycan, the major and essential structural component of the cell wall. Although the biochemical composition of peptidoglycan is well understood, how the peptidoglycan architecture can accommodate the dynamics of growth and division while maintaining cell shape remains largely unknown. Here, we elucidate the peptidoglycan architecture and dynamics of bacteria with ovoid cell shape (ovococci), which includes a number of important pathogens, by combining biochemical analyses with atomic force and super‐resolution microscopies. Atomic force microscopy analysis showed preferential orientation of the peptidoglycan network parallel to the short axis of the cell, with distinct architectural features asso... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397533 Mon, 07 Nov 2011 05:00:00 +0100 5397533 http://www.medworm.com/index.php?rid=5397532&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07873.x SummaryLysine acetylation is a well‐established post‐translational modification widely conserved and distributed in bacteria. Although multiple regulatory roles have been proved, little is known about its regulation. Here, we present evidence that the transcription of the Gcn5‐like acetyltransferase YfiQ of Escherichia coli (proposed name: PatZ) is regulated by cAMP‐CRP and its implications on acetate metabolism regulation. The acetate scavenging acetyl‐CoA synthetase (Acs) is regulated at the transcriptional and post‐translational levels. Post‐translational regulation depends on a protein acetyltransferase (yfiQ) and an NAD+‐dependent deacetylase (cobB). We have studied their expression under different environmental conditions. cobB is constitutively expressed from a promo... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397532 Mon, 07 Nov 2011 05:00:00 +0100 5397532 http://www.medworm.com/index.php?rid=5397531&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07875.x In this study we identify a gene cluster involved in the biosynthesis of sulfoquinovose and important for the assembly of the S‐layer N‐glycans. A successful markerless in‐frame deletion of agl3 resulted in a decreased molecular mass of the S‐layer glycoprotein SlaA and the flagellin FlaB, indicating a change in the N‐glycan composition. Analyses with nanoLC ES‐MS/MS confirmed the presence of only a reduced trisaccharide structure composed of Man1GlcNAc2, missing the sulfoquinovose, a mannose and glucose. Biochemical studies of the recombinant Agl3 confirmed the proposed function as a UDP‐sulfoquinovose synthase. Furthermore, S. acidocaldarius cells lacking agl3 had a significantly lower growth rate at elevated salt concentrations compared with the background strain, underl... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397531 Mon, 07 Nov 2011 05:00:00 +0100 5397531 http://www.medworm.com/index.php?rid=5397530&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07878.x This study has investigated the role of the hybrid histidine kinase components encoded by drkA and slnA, in the dimorphic pathogen Penicillium marneffei. Both SlnA and DrkA are required for stress adaptation but are uniquely required for different aspects of asexual development, hyphal morphogenesis and cell wall integrity. Importantly, slnA and drkA are both essential for the generation of yeast cells in vivo, with slnA required for the germination of conidia and drkA required for dimorphic switching during macrophage infection. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397530 Mon, 07 Nov 2011 05:00:00 +0100 5397530 http://www.medworm.com/index.php?rid=5397529&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07879.x SummaryToxoplasma gondii is an obligate intracellular parasite of all warm‐blooded animals. We previously described a forward genetic screen to identify T. gondii mutants defective in the establishment of a chronic infection. One of the mutants isolated was disrupted in the 3′ untranslated region (3′UTR) of an orthologue of bacterial translation elongation factor G (EFG). The mutant does not have a growth defect in tissue culture. Genetic complementation of this mutant with the genomic locus of TgEFG restores virulence in an acute infection mouse model. Epitope tagged TgEFG localized to the apicoplast, via a non‐canonical targeting signal, where it functions as an elongation factor for translation in the apicoplast. Comparisons of TgEFG expression constructs with wild‐type or m... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397529 Mon, 07 Nov 2011 05:00:00 +0100 5397529 http://www.medworm.com/index.php?rid=5397528&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07890.x SummaryMany bacteria are now believed to produce small signal molecules in order to communicate in a process called quorum sensing (QS), which mediates cooperative traits and a co‐ordinated behaviour. Pseudomonads have been extensively studied for their QS response highlighting that it plays a major role in determining their lifestyle. The main QS signal molecules produced by Pseudomonas belong to the family of N‐acyl‐homoserine lactones (AHLs); these are synthesized by a LuxI‐family synthase and sensed by a LuxR‐family regulator. Most often in Pseudomonas, repressor genes intergenically located between luxI and luxR form an integral part of QS system. Recent studies have highlighted an important role of these repressors (called RsaL and RsaM) in containing the QS response within... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397528 Mon, 07 Nov 2011 05:00:00 +0100 5397528 http://www.medworm.com/index.php?rid=5397521&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07903.x ABSTRACTType IVa pili are bacterial nanomachines required for colonization of surfaces, but little is known about the organization of proteins in this system. The Pseudomonas aeruginosa pilMNOPQ operon encodes five key members of the transenvelope complex facilitating pilus function. While PilQ forms the outer membrane secretin pore, the functions of the inner membrane‐associated proteins PilM/N/O/P are less well defined. Structural characterization of a stable C‐terminal fragment of PilP (PilPΔ71) by NMR revealed a modified β‐sandwich fold, similar to that of Neisseria meningitidis PilP, although complementation experiments showed that the two proteins are not interchangeable likely due to divergent surface properties. PilP is an inner membrane putative lipoprotein, but mutagenesi... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397521 Mon, 07 Nov 2011 05:00:00 +0100 5397521 http://www.medworm.com/index.php?rid=5397520&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07909.x SummaryThe attachment of bacteria to surfaces provides advantages such as increasing nutrient access and resistance to environmental stress. Attachment begins with a reversible phase, often mediated by surface structures such as flagella and pili, followed by a transition to irreversible attachment, typically mediated by polysaccharides. Here we show that the interplay between pili and flagellum rotation stimulates the rapid transition between reversible and polysaccharide‐mediated irreversible attachment. We found that reversible attachment of Caulobacter crescentus cells is mediated by motile cells bearing pili and that their contact with a surface results in the rapid pili‐dependent arrest of flagellum rotation and concurrent stimulation of polar holdfast adhesive polysaccharide. Si... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397520 Mon, 07 Nov 2011 05:00:00 +0100 5397520 http://www.medworm.com/index.php?rid=5397519&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07910.x SummaryHelicobacter pylori (H. pylori) infection is an etiologic cause of gastric disorders worldwide. H. pylori has been shown to assimilate and convert host cholesterol into cholesteryl glucosides (CGs) by cholesterol‐α‐glucosyltransferase encoded by capJ. Here, we show that capJ‐knockout (ΔcapJ) H. pylori resulted in greatly reduced type IV secretion system (TFSS)‐associated activities, including the hummingbird phenotype of AGS cells, IL‐8 production, CagA translocation/phosphorylation and CagA‐mediated signaling events. Complementation of the ΔcapJ mutation by using a knock‐in mutant or adding the CGs‐containing lysates or exogenous fluorophore‐tagged CGs restored the abrogated phenotypes. We also show that the wild‐type but not ΔcapJ H. pylori recruited raft�... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397519 Mon, 07 Nov 2011 05:00:00 +0100 5397519 http://www.medworm.com/index.php?rid=5397518&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07912.x SUMMARYThe Crc protein is a translational repressor that recognizes a specific target at some mRNAs, controlling catabolite repression and coordinating carbon metabolism in pseudomonads. In Pseudomonas aeruginosa, the levels of free Crc protein are controlled by CrcZ, a sRNA that sequesters Crc, acting as an antagonist. We show that, in Pseudomonas putida, the levels of free Crc are controlled by CrcZ and by a novel 368 nt sRNA named CrcY. CrcZ and CrcY, which contain six potential targets for Crc, were able to bind Crc specifically in vitro. The levels of CrcZ and CrcY were low under conditions generating a strong catabolite repression, and increased strongly when catabolite repression was absent. Deletion of either crcZ or crcY had no effect on catabolite repression, but the simultaneous... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397518 Mon, 07 Nov 2011 05:00:00 +0100 5397518 http://www.medworm.com/index.php?rid=5397517&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07918.x SummaryIn lipopolysaccharide (LPS) biosynthesis of Gram‐negative bacteria the lipid A‐core oligosaccharide (LA‐core) and O‐polysaccharide (O‐PS) biosynthesis pathways proceed separately and converge in periplasmic space where the waaL‐encoded ligase joins O‐PS onto LA‐core. Enterobacterial common antigen (ECA) biosynthesis follows that of O‐PS except that ECA is usually ligated to phosphatidylglycerol (PG) and only rarely to LA‐core. In Yersinia enterocolitica serotype O:3 LPS is composed of LA‐inner core (IC) onto which a homopolymeric O‐PS, a hexasaccharide called outer core (OC), and/or ECA are ligated. We found that an individual O:3 LPS‐molecule carries either OC‐ or O‐PS‐substitution but not both. Related to this, we identified three genes in Y. entero... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397517 Mon, 07 Nov 2011 05:00:00 +0100 5397517 http://www.medworm.com/index.php?rid=5376539&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07876.x In this study, we demonstrate meningococcal interactions with vitronectin via a novel adhesin, Msf (meningococcal surface fibril, previously NhhA or Hsf). As with Opc, Msf binds preferentially to activated vitronectin (aVn), engaging at its N‐terminal region but the C‐terminal heparin binding domain may also participate. However, unlike Opc, the latter binding is not heparin‐mediated. By binding to aVn, Msf or Opc can impart serum resistance, which is further increased in coexpressers, a phenomenon dependent on serum aVn concentrations. The survival fitness of aVn‐binding derivatives was evident from mixed population studies, in which msf/opc mutants were preferentially depleted. In addition, using vitronectin peptides to block Msf–aVn interactions, aVn‐induced inhibition of ly... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5376539 Fri, 04 Nov 2011 04:00:00 +0100 5376539 http://www.medworm.com/index.php?rid=5376540&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07893.x SummaryHET‐s is a prion protein of the filamentous fungus Podospora anserina. An orthologue of this protein, called FgHET‐s has been identified in Fusarium graminearum. The region of the FgHET‐s protein corresponding to the prion forming domain of HET‐s, forms amyloid fibrils in vitro. These fibrils seed HET‐s(218–289) fibril formation in vitro and vice versa. The amyloid fold of HET‐s(218–289) and FgHET‐s(218–289) are remarkably similar although they share only 38% identity. The present work corresponds to the functional characterization of the FgHET‐s(218–289) region as a prion forming domain in vivo. We show that FgHET‐s(218–289) is capable of prion propagation in P. anserina and is able to substitute for the HET‐s PFD in the full‐length HET‐s protein... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5376540 Thu, 03 Nov 2011 04:00:00 +0100 5376540 http://www.medworm.com/index.php?rid=5404955&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07917.x Swarming motility is the movement of bacteria over a solid surface powered by rotating flagella. The expression of flagellar biosynthesis genes is governed by species‐specific master regulator transcription factors. Mutations that reduce or enhance master regulator activity have a commensurate effect on swarming motility. Here we review what is known about the proteins that modulate swarming motility and appear to act upstream of the master flagellar regulators in diverse swarming bacteria. We hypothesize that environmental control of the master regulators is important to the swarming phenotype perhaps at the level of controlling flagellar number. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5404955 Tue, 01 Nov 2011 04:00:00 +0100 5404955 http://www.medworm.com/index.php?rid=5397516&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07919.x We present here the 2.2 Å X‐ray crystal structure of full‐length AphB. As reported for other LysR‐type proteins, AphB is a tetramer with two distinct subunit conformations. Unlike other family members, AphB must undergo a significant conformational change in order to bind to DNA. We have found five independent mutations in the putative ligand‐binding pocket region that allow AphB to constitutively activate tcpPH expression at the non‐permissive pH of 8.5 and in the presence of oxygen. These findings indicate that AphB is responsive to intracellular pH as well as to anaerobiosis and that residues in the ligand‐binding pocket of the protein influence its ability to respond to both of these signals. We have solved the structure of one of the constitutive mutants, and observe conf... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397516 Tue, 01 Nov 2011 04:00:00 +0100 5397516 http://www.medworm.com/index.php?rid=5376530&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07907.x SUMMARYA major class of small bacterial RNAs (sRNAs) regulate translation and mRNA stability by pairing with target mRNAs, dependent upon the RNA chaperone Hfq. Hfq, related to the Lsm/Sm families of splicing proteins, binds the sRNAs and stabilizes them in vivo and stimulates pairing with mRNAs in vitro. Although Hfq is abundant, the sRNAs, when induced, are similarly abundant. Therefore, Hfq may be limiting for sRNA function. We find that, when overexpressed, a number of sRNAs competed with endogenous sRNAs for binding to Hfq. This correlated with lower accumulation of the sRNAs (presumably a reflection of the loss of Hfq binding), and lower activity of the sRNAs in regulating gene expression. Hfq was limiting for both positive and negative regulation by the sRNAs. In addition, deletion ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5376530 Tue, 01 Nov 2011 04:00:00 +0100 5376530 http://www.medworm.com/index.php?rid=5437723&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07902.x SummaryStreptococcal pyrogenic exotoxin B (SpeB) is an extracellular cysteine protease that is a critical virulence factor made by the major human pathogen group A Streptococcus (GAS). speB expression is dependent on the regulator of proteinase B (RopB) and is upregulated with increasing cell density and during infection. Because computer modelling suggested significant structural similarity between RopB and peptide‐sensing regulatory proteins made by other Gram‐positive bacteria, we hypothesized that speB expression is influenced by RopB–peptide interactions. Inactivation of the gene (vfr) encoding the virulence factor related (Vfr) protein resulted in increased speB transcript level during the exponential growth phase, whereas provision of only the amino‐terminal region of Vfr co... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5437723 Mon, 31 Oct 2011 04:00:00 +0100 5437723 http://www.medworm.com/index.php?rid=5437722&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07906.x SummaryAssimilatory and dissimilatory sulphite reductions are key reactions in the biogeochemical sulphur cycle and several distinct sirohaem‐containing sulphite reductases have been characterized. Here, we describe that the Epsilonproteobacterium Wolinella succinogenes is able to grow by sulphite respiration (yielding sulphide) with formate as electron donor. Sulphite is reduced by MccA, a prototypical member of an emerging new class of periplasmic cytochrome c sulphite reductases that, phylogenetically, belongs to a multihaem cytochrome c superfamily whose members play crucial roles in the global sulphur and nitrogen cycles. Within this family, MccA represents an unconventional octahaem cytochrome c containing a special haem c group that is bound via two cysteine residues arranged in a... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5437722 Mon, 31 Oct 2011 04:00:00 +0100 5437722 http://www.medworm.com/index.php?rid=5418540&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07905.x This study reveals a possible novel dissemination mechanism utilized by pathogens. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5418540 Mon, 31 Oct 2011 04:00:00 +0100 5418540 http://www.medworm.com/index.php?rid=5404958&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07901.x SummaryCell‐surface signalling systems are widespread in Gram‐negative bacteria. In these systems gene expression occurs following binding of a ligand, commonly a siderophore, to a receptor protein in the outer membrane. The receptor interacts with a sigma regulator protein that extends from the periplasm into the cytoplasm to control the activity of a cognate sigma factor. The mechanisms of signal transduction in cell‐surface signalling systems have not been determined. Here we investigate signal transduction in the pyoverdine, ferrichrome and desferrioxamine siderophore systems of Pseudomonas aeruginosa. When pyoverdine is present the sigma regulator FpvR undergoes complete proteolysis resulting in activation of two sigma factors PvdS and FpvI and expression of genes for pyoverdine... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5404958 Mon, 31 Oct 2011 04:00:00 +0100 5404958 http://www.medworm.com/index.php?rid=5376536&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07901.x SummaryCell‐surface signaling systems are widespread in Gram‐negative bacteria. In these systems gene expression occurs following binding of a ligand, commonly a siderophore, to a receptor protein in the outer membrane. The receptor interacts with a sigma regulator protein that extends from the periplasm into the cytoplasm to control the activity of a cognate sigma factor. The mechanisms of signal transduction in cell surface signaling systems have not been determined. Here we investigate signal transduction in the pyoverdine, ferrichrome and desferrioxamine siderophore systems of Pseudomonas aeruginosa. When pyoverdine is present the sigma regulator FpvR undergoes complete proteolysis resulting in activation of two sigma factors PvdS and FpvI and expression of genes for pyoverdine syn... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5376536 Mon, 31 Oct 2011 04:00:00 +0100 5376536 http://www.medworm.com/index.php?rid=5376535&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07902.x SUMMARYStreptococcal pyrogenic exotoxin B (SpeB) is an extracellular cysteine protease that is a critical virulence factor made by the major human pathogen group A Streptococcus (GAS). speB expression is dependent on the regulator of proteinase B (RopB) and is upregulated with increasing cell density and during infection. Because computer modeling suggested significant structural similarity between RopB and peptide‐sensing regulatory proteins made by other Gram‐positive bacteria, we hypothesized that speB expression is influenced by RopB‐peptide interactions. Inactivation of the gene (vfr) encoding the virulence factor related (Vfr) protein resulted in increased speB transcript level during the exponential growth phase, whereas provision of only the amino‐terminal region of Vfr com... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5376535 Mon, 31 Oct 2011 04:00:00 +0100 5376535 http://www.medworm.com/index.php?rid=5376533&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07904.x We report here that a subpopulation of ubiquitylated yeast SOD1 and other ubiquitylated mammalian proteins activate ExoU. Phospholipase activity was detected using purified ubiquitin of various chain lengths and linkage types; however, free monoubiquitin is sufficient in a genetically engineered dual expression system. The use of ubiquitin by a bacterial enzyme as an activator is unprecedented and represents a new aspect in the manipulation of the eukaryotic ubiquitin system to facilitate bacterial replication and dissemination. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5376533 Mon, 31 Oct 2011 04:00:00 +0100 5376533 http://www.medworm.com/index.php?rid=5376532&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07905.x This study reveals a possible novel dissemination mechanism utilized by pathogens. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5376532 Mon, 31 Oct 2011 04:00:00 +0100 5376532 http://www.medworm.com/index.php?rid=5376531&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07906.x SummaryAssimilatory and dissimilatory sulfite reduction are key reactions in the biogeochemical sulfur cycle and several distinct sirohaem‐containing sulfite reductases have been characterized. Here, we describe that the Epsilonproteobacterium Wolinella succinogenes is able to grow by sulfite respiration (yielding sulfide) with formate as electron donor. Sulfite is reduced by MccA, a prototypical member of an emerging new class of periplasmic cytochrome c sulfite reductases that, phylogenetically, belongs to a multihaem cytochrome c superfamily whose members play crucial roles in the global sulfur and nitrogen cycles. Within this family, MccA represents an unconventional octahaem cytochrome c containing a special haem c group that is bound via two cysteine residues arranged in a unique C... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5376531 Mon, 31 Oct 2011 04:00:00 +0100 5376531 http://www.medworm.com/index.php?rid=5356010&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07900.x ABSTRACTThe biogenesis of ER Exit Site/Golgi Junctions (EGJ) in bloodstream form African trypanosomes is investigated using tagged markers for ER Exit Sites, the Golgi, and the bilobe structure. The typical pattern is two EGJ in G1 phase (1 kinetoplast/1 nucleus, 1K1N) through S phase (2K1N), duplication to four EGJ in post‐mitotic cells (2K2N), and segregation of two EGJ to each daughter. Lesser cell percentages have elevated EGJ copy numbers in all stages, and blocking cell cycle progression results in even higher copy numbers. EGJs are closely aligned with the flagellar attachment zone (FAZ) indicating nucleation on the FAZ‐associated ER (FAZ:ER). Only the most posterior EGJ in each cell is in proximity to the bilobe, which is located at the base of the FAZ filament near the mouth o... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356010 Fri, 28 Oct 2011 07:20:48 +0100 5356010 http://www.medworm.com/index.php?rid=5356020&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07867.x This study provides new insights into biofilm development and transmission of biofilm‐derived V. cholerae. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356020 Thu, 27 Oct 2011 04:00:00 +0100 5356020 http://www.medworm.com/index.php?rid=5356019&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07880.x In this study we examined the import pathway of a pathogenic bacterial protein, PorB, which is targeted from pathogenic Neisseria to the host mitochondria. We have developed a new method for measurement of PorB assembly into mitochondria that relies on the mobility shift exhibited by bacterial β‐barrel proteins once folded and separated under semi‐native electrophoretic conditions. We show that PorB is targeted to the outer mitochondrial membrane with a dependence on the intermembrane space shuttling chaperones and the core component of the SAM, Sam50, which is a functional homologue of BamA that is required for PorB assembly in bacteria. The peripheral subunits of the SAM, Sam35 and Sam37, which are essential for eukaryotic β‐barrel protein assembly but do not have distinguishable... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356019 Thu, 27 Oct 2011 04:00:00 +0100 5356019 http://www.medworm.com/index.php?rid=5356018&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07881.x SummaryPlant pathogenic bacteria of the genera Dickeya and Pectobacterium are broad‐host‐range necrotrophs which cause soft‐rot diseases in important crops. A metabolomic analysis, based on 13C‐NMR spectroscopy, was used to characterize the plant‐bacteria interaction. Metabolic profiles revealed a decline in plant sugars and amino acids during infection and the concomitant appearance of a compound identified as 2,3‐butanediol. Butanediol is the major metabolite found in macerated tissues of various host plants. It is accumulated during the symptomatic phase of the disease. Different species of Dickeya or Pectobacterium secrete high levels of butanediol during plant infection. Butanediol has been described as a signalling molecule involved in plant/bacterium interactions and, no... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356018 Thu, 27 Oct 2011 04:00:00 +0100 5356018 http://www.medworm.com/index.php?rid=5356017&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07882.x SummaryArsenate reductases (ArsCs) evolved independently as a defence mechanism against toxic arsenate. In the genome of Corynebacterium glutamicum, there are two arsenic resistance operons (ars1 and ars2) and four potential genes coding for arsenate reductases (Cg_ArsC1, Cg_ArsC2, Cg_ArsC1' and Cg_ArsC4). Using knockout mutants, in vitro reconstitution of redox pathways, arsenic measurements and enzyme kinetics, we show that a single organism has two different classes of arsenate reductases. Cg_ArsC1 and Cg_ArsC2 are single‐cysteine monomeric enzymes coupled to the mycothiol/mycoredoxin redox pathway using a mycothiol transferase mechanism. In contrast, Cg_ArsC1' is a three‐cysteine containing homodimer that uses a reduction mechanism linked to the thioredoxin pathway with a kcat/KM v... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356017 Thu, 27 Oct 2011 04:00:00 +0100 5356017 http://www.medworm.com/index.php?rid=5397524&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07897.x SummaryPhage T4, the archetype of lytic bacterial viruses, needs only 62 genes to propagate under standard laboratory conditions. Interestingly, the T4 genome contains more than 100 putative genes of unknown function, with few detectable homologues in cellular genomes. To characterize this uncharted territory of genetic information, we have identified several T4 genes that prevent bacterial growth when expressed from plasmids under inducible conditions. Here, we report on the various phenotypes and molecular characterization of 55.1, one of the genes of unknown function. High‐level expression from the arabinose‐inducible PBAD promoter is toxic to the bacteria and delays the intracellular accumulation of phage without affecting the final burst size. Low‐level expression from T4 promot... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397524 Wed, 26 Oct 2011 04:00:00 +0100 5397524 http://www.medworm.com/index.php?rid=5397522&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07900.x SummaryThe biogenesis of the ER Exit Site/Golgi Junction (EGJ) in bloodstream‐form African trypanosomes is investigated using tagged markers for ER Exit Sites, the Golgi and the bilobe structure. The typical pattern is two EGJ in G1 phase (1 kinetoplast/1 nucleus, 1K1N) through S‐phase (2K1N), duplication to four EGJ in post‐mitotic cells (2K2N) and segregation of two EGJ to each daughter. Lesser cell percentages have elevated EGJ copy numbers in all stages, and blocking cell cycle progression results in even higher copy numbers. EGJs are closely aligned with the flagellar attachment zone (FAZ) indicating nucleation on the FAZ‐associated ER (FAZ:ER). Only the most posterior EGJ in each cell is in proximity to the bilobe, which is located at the base of the FAZ filament near the mou... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5397522 Wed, 26 Oct 2011 04:00:00 +0100 5397522 http://www.medworm.com/index.php?rid=5356016&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07874.x AbstractMagnetotactic bacteria navigate along magnetic field lines using well‐ordered chains of membrane‐enclosed magnetic crystals, referred to as magnetosomes, which have emerged as model to investigate organelle biogenesis in prokaryotic systems. To become divided and segregated faithfully during cytokinesis, the magnetosome chain has to be properly positioned, cleaved and separated against intrachain magnetostatic forces.Here we demonstrate that magnetotactic bacteria use dedicated mechanisms to control the position and division of the magnetosome chain, thus maintaining magnetic orientation throughout divisional cycle. Using electron and time‐lapse microscopy of synchronized cells of Magnetospirillum gryphiswaldense, we show that magnetosome chains undergo a dynamic pole‐to‐... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356016 Wed, 26 Oct 2011 04:00:00 +0100 5356016 http://www.medworm.com/index.php?rid=5356015&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07887.x SummaryIn Gram‐positive bacteria proteins are displayed on the cell surface using sortase enzymes. These cysteine transpeptidases join proteins bearing an appropriate sorting signal to strategically positioned amino groups on the cell surface. Working alone, or in concert with other enzymes, sortases either attach proteins to the cross‐bridge peptide of the cell wall or they link proteins together to form pili. Because surface proteins play a fundamental role in microbial physiology and are frequently virulence factors, sortase enzymes have been intensely studied since their discovery a little more than a decade ago. Based on their primary sequences and functions sortases can be partitioned into distinct families called class A to F enzymes. Most bacteria elaborate their surfaces using... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356015 Wed, 26 Oct 2011 04:00:00 +0100 5356015 http://www.medworm.com/index.php?rid=5356014&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07892.x AbstractNADH pyrophosphatase (NudC) catalyzes the hydrolysis of NAD(H) to AMP and NMN(H) [nicotinamide mononucleotide (reduced form)]. NudC multiple sequence alignment reveals that homologues from most Mycobacterium tuberculosis isolates, but not other mycobacterial species, have a polymorphism at the highly conserved residue 237. To elucidate the functional significance of this polymorphism, comparative analyses were performed using representative NudC isoforms from M. tuberculosis H37Rv (NudCRv) and M. bovis BCG (NudCBCG). Biochemical analysis showed that the P237Q polymorphism prevents dimer formation, and results in a loss of enzymatic activity. Importantly, NudCBCG was found to degrade the active forms of isoniazid (INH), INH‐NAD and ethionamide (ETH), ETH‐NAD. Consequently, over�... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356014 Wed, 26 Oct 2011 04:00:00 +0100 5356014 http://www.medworm.com/index.php?rid=5356013&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07895.x SummaryThe endonuclease RNase E of Escherichia coli is essential for viability, but deletion of its C‐terminal half (CTH) is not lethal. RNase E preferentially acts on 5′‐monophosphorylated RNA whose generation from primary transcripts is catalyzed by RppH, but ΔRppH strains are viable. Here we show that the RNase E‐ΔCTH ΔRppH combination is lethal, and that the lethality is suppressed by rho or nusG mutations impairing Rho‐dependent transcription termination. Lethality was correlated with defects in bulk mRNA decay and tRNA processing, which were reversed by the rho suppressor. Lethality suppression was dependent on RNase H1 or the helicase UvsW of phage T4, both of which act to remove RNA‐DNA hybrids (R‐loops). The rho and nusG mutations also rescued inviability of a dou... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356013 Wed, 26 Oct 2011 04:00:00 +0100 5356013 http://www.medworm.com/index.php?rid=5356012&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07897.x SummaryPhage T4, the archetype of lytic bacterial viruses, needs only 62 genes to propagate under standard laboratory conditions. Interestingly, the T4 genome contains more than 100 putative genes of unknown function, with few detectable homologues in cellular genomes. To characterize this uncharted territory of genetic information, we have identified several T4 genes that prevent bacterial growth when expressed from plasmids under inducible conditions. Here, we report on the various phenotypes and molecular characterization of 55.1, one of the genes of unknown function. High‐level expression from the arabinose‐inducible PBAD promoter is toxic to the bacteria and delays the intracellular accumulation of phage without affecting the final burst size. Low‐level expression from T4 promot... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356012 Wed, 26 Oct 2011 04:00:00 +0100 5356012 http://www.medworm.com/index.php?rid=5356011&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07898.x AbstractBacterial genomes are functionally organized. This organization is dynamic and globally changing throughout the cell cycle. Upon initiation of replication of the chromosome, the two origins segregate and move towards their new location taking along the newly replicated genome. Caulobacter crescentus employs a dedicated active partitioning (Par) system to move one copy of the parS centromere to the distal pole, while the other stays at the stalked pole. In this issue of Molecular Microbiology, Hong & McAdams describe studies on the speed of segregation of parS and regions up to 150kb away. They show clear differences in segregation rates between parS and 50 kb flanking regions versus regions further away. To assess segregation rates the authors track fluorescent markers during m... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356011 Wed, 26 Oct 2011 04:00:00 +0100 5356011 http://www.medworm.com/index.php?rid=5344023&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07889.x SummaryProductive intercellular delivery of cargo by secretory systems requires exquisite temporal and spatial choreography. Our laboratory has demonstrated that the hemolysin co‐regulated secretion island I (HSI‐I)‐encoded type VI secretion system (H1‐T6SS) of Pseudomonas aeruginosa transfers effector proteins to other bacterial cells. The activity of these effectors requires cell contact‐dependent delivery by the secretion apparatus, and thus their export is highly repressed under planktonic growth conditions. Here we define regulatory pathways that orchestrate efficient secretion by this system. We identified a T6S‐associated protein, TagF, as a posttranslational repressor of the H1‐T6SS. Strains activated by TagF derepression or stimulation of a previously identified thre... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5344023 Mon, 24 Oct 2011 12:10:30 +0100 5344023 http://www.medworm.com/index.php?rid=5356026&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07862.x SummaryZinc is an essential trace metal for living cells. The ABC transporter AdcABC was previously shown to be required for zinc uptake by Streptococcus pneumoniae. As we have recently described AdcAII as another zinc‐binding lipoprotein, we have investigated the role of both AdcA and AdcAII in S. pneumoniae zinc metabolism. Deletion of either adcA or adcAII but not phtD reduced S. pneumoniae zinc uptake, with dual mutation of both adcA and adcAII further decreasing zinc import. For the Δ(adcA/adcAII) mutant, growth and intracellular concentrations of zinc were both greatly reduced in low zinc concentration. When grown in zinc‐deficient medium, the Δ(adcA/adcAII) mutant displayed morphological defects related to aberrant septation. Growth and morphology of the Δ(adcA/adcAII) mu... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356026 Mon, 24 Oct 2011 04:00:00 +0100 5356026 http://www.medworm.com/index.php?rid=5356025&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07868.x SummaryMoulds are characterized by their saprophytic lifestyle that is based on osmotrophy. Among them, Aspergillus fumigatus has emerged as the leading cause of fungal infections in the presence of an underlying immunodeficiency. To assess the role of its nutritional versatility for virulence, transcriptional profiling studies in the presence of varying sources of nitrogen were carried out and revealed an extensive reprogramming of the fungal transcriptome when shifting to a proteinaceous growth substrate. Transcripts encoding metabolic activities were predominantly upregulated, as were proteinases and transport activities. To probe whether fundamental aspects of its osmotrophic lifestyle, that is, extracellular proteolysis and uptake of oligopeptides, are required for A. fumigatus path... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356025 Mon, 24 Oct 2011 04:00:00 +0100 5356025 http://www.medworm.com/index.php?rid=5356024&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07865.x In this study, we analyse the IF amino acid residues involved in GS inactivation by a mutational approach, both in vitro and in vivo. The results clearly indicate that the GS–IF complex formation must be determined mainly by electrostatic interactions. We have identified three conserved arginine residues of IF7 and IF17 that are essential for the interaction of these proteins with GS. All these residues map in the homologous region of IFs. Furthermore, in vitro analysis of a truncated IF17 protein without the 82‐residue‐long amino‐terminal part, together with the analysis of a Synechocystis strain expressing a chimeric protein, containing this amino‐terminal part of IF17 fused to IF7, demonstrates that amino‐terminal region of IF17 mostly confers a higher stability to this prot... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356024 Mon, 24 Oct 2011 04:00:00 +0100 5356024 http://www.medworm.com/index.php?rid=5356023&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07884.x SummarySalmonella Typhimurium combats phagocytic superoxide by producing the periplasmic superoxide dismutase, SodCI. The homologous protein, SodCII, is also produced during infection, but does not contribute to virulence. The proteins physically differ in that SodCI is dimeric, protease resistant and non‐covalently tethered within the periplasm. Conversely, SodCII is a protease‐sensitive monomer that is released normally from the periplasm by osmotic shock. To identify which properties correlate with virulence, we constructed over 20 enzymatically functional hybrid SodC proteins and assayed them for protease susceptibility, release by osmotic shock, multimerization and affinity for metal cofactors. Protease susceptibility maps to the C‐terminus of SodCII, while SodCI residues 120–... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356023 Mon, 24 Oct 2011 04:00:00 +0100 5356023 http://www.medworm.com/index.php?rid=5356022&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07869.x In conclusion, subcellular localization of PHB granules in R. eutropha depends on a concerted expression of at least three PHB granule‐associated proteins, namely PhaM, PhaP5 and PHB synthase PhaC1. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356022 Mon, 24 Oct 2011 04:00:00 +0100 5356022 http://www.medworm.com/index.php?rid=5356021&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07870.x SummaryBacteria communicate with each other through contact‐independent and ‐dependent signalling mechanisms. Sensory perception of both types of signals is needed for conjugative transfer of mobile DNA elements via type IV secretion systems (T4SSs) to bacterial or eukaryotic target cells. While the regulatory circuitries coupling extracellular quorum and environmental signals to transcription of T4SS genes are increasingly understood, it remains fundamentally unknown how a potential recipient cell stimulates donor conjugative DNA transfer upon contact. In this issue, Zechner and colleagues report use of the male‐specific bacteriophage R17, a phage that binds conjugative pili elaborated by IncF plasmid R1, to define requirements for phage‐contact‐mediated T4SS activation and phag... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5356021 Mon, 24 Oct 2011 04:00:00 +0100 5356021 http://www.medworm.com/index.php?rid=5376542&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07888.x SummaryThe presence of very different sets of enzymes, and in particular the presence of RNase E and RNase J, has been used to explain significant differences in RNA metabolism between the two model organisms Escherichia coli and Bacillus subtilis. However, these studies might have somewhat polarized our view of RNA metabolism. Here, we identified a RNase J in Mycobacterium smegmatis that has both 5′‐3′ exo‐ and endonucleolytic activity. This enzyme coexists with RNase E in this organism, a configuration that enabled us to study how these two key nucleases collaborate. We demonstrate that RNase E is responsible for the processing of the furA‐katG transcript in M. smegmatis and that both RNase E and RNase J are involved in the 5′ end processing of all ribosomal RNAs. In contra... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5376542 Thu, 20 Oct 2011 04:00:00 +0100 5376542 http://www.medworm.com/index.php?rid=5376538&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07889.x SummaryProductive intercellular delivery of cargo by secretory systems requires exquisite temporal and spatial choreography. Our laboratory has demonstrated that the haemolysin co‐regulated secretion island I (HSI‐I)‐encoded type VI secretion system (H1‐T6SS) of Pseudomonas aeruginosa transfers effector proteins to other bacterial cells. The activity of these effectors requires cell contact‐dependent delivery by the secretion apparatus, and thus their export is highly repressed under planktonic growth conditions. Here we define regulatory pathways that orchestrate efficient secretion by this system. We identified a T6S‐associated protein, TagF, as a posttranslational repressor of the H1‐T6SS. Strains activated by TagF derepression or stimulated through a previously identified... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5376538 Thu, 20 Oct 2011 04:00:00 +0100 5376538 http://www.medworm.com/index.php?rid=5344027&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07877.x SummaryChlamydia trachomatis is an obligate intracellular pathogen responsible for ocular and genital infections of significant public health importance. C. trachomatis undergoes a biphasic developmental cycle alternating between two distinct forms: the infectious elementary body (EB), and the replicative but non‐infectious reticulate body (RB). The molecular basis for these developmental transitions and the metabolic properties of the EB and RB forms are poorly understood as these bacteria have traditionally been difficult to manipulate through classical genetic approaches. Using two‐dimensional liquid chromatography – tandem mass spectrometry (LC/LC‐MS/MS) we performed a large‐scale, label‐free quantitative proteomic analysis of C. trachomatis LGV‐L2 EB and RB forms. Additi... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5344027 Thu, 20 Oct 2011 04:00:00 +0100 5344027 http://www.medworm.com/index.php?rid=5344026&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07885.x SummaryEhrlichia chaffeensis is an obligate intracellular bacterium that causes human monocytic ehrlichiosis. Ehrlichiae have a biphasic developmental cycle consisting of dense‐cored cells (DCs) and reticulate cells (RCs). Isolated DCs are more stress resistant and infectious than RCs. Here, we report that a response regulator, CtrA was upregulated in human monocytes at the late growth stage when DCs develop. E. chaffeensis CtrA bound to the promoters of late‐stage transcribed genes: ctrA, ompA (peptidoglycan‐associated lipoprotein), bolA (stress‐induced morphogen), and surE (stationary phase survival protein), which contain CtrA‐binding motifs, and transactivated ompA, surE, and bolA promoter‐lacZ fusions in Escherichia coli. OmpA was predominantly expressed in DCs. E. chaffee... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5344026 Thu, 20 Oct 2011 04:00:00 +0100 5344026 http://www.medworm.com/index.php?rid=5344025&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07888.x SummaryThe presence of very different sets of enzymes, and in particular the presence of RNase E and RNase J, has been used to explain significant differences in RNA metabolism between the two model organisms E. coli and B. subtilis. However, these studies might have somewhat polarized our view of RNA metabolism. Here, we identified a RNase J in M. smegmatis that has both 5’‐3’ exo‐ and endonucleolytic activity. This enzyme co‐exists with RNase E in this organism, a configuration that enabled us to study how these two key nucleases collaborate. We demonstrate that RNase E is responsible for the processing of the furA‐katG transcript in M. smegmatis and that both RNase E and RNase J are involved in the 5’‐end processing of all ribosomal RNAs. In contrast to B. subtilis, the ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5344025 Thu, 20 Oct 2011 04:00:00 +0100 5344025 http://www.medworm.com/index.php?rid=5344024&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07891.x SummaryNickel is toxic to all forms of life, but the mechanisms of cell damage are unknown. Indeed, environmentally relevant nickel levels (8 μM) inhibit wild‐type Escherichia coli growth on glucose minimal medium. The same concentration of nickel also inhibits growth on fructose, but not succinate, lactate, or glycerol; these results suggest that fructose‐1,6‐bisphosphate aldolase (FbaA) is a target of nickel toxicity. Cells stressed by 8 μM Ni(II) for 20 min lost 75% of their FbaA activity, demonstrating that FbaA is inactivated during nickel stress. Furthermore, over‐expression of fbaA restored growth in glucose minimal medium supplemented with 8 μM Ni(II), thus confirming that FbaA is a primary target of nickel toxicity. This class II aldolase has an active site zinc and a n... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5344024 Thu, 20 Oct 2011 04:00:00 +0100 5344024 http://www.medworm.com/index.php?rid=5331374&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07863.x SummaryMagnetotactic bacteria form chains of intracellular membrane‐enclosed, nanometre‐sized magnetite crystals for navigation along the earth's magnetic field. The assembly of these prokaryotic organelles requires several specific polypeptides. Among the most abundant proteins associated with the magnetosome membrane of Magnetospirillum gryphiswaldense are MamB and MamM, which were implicated in magnetosomal iron transport because of their similarity to the cation diffusion facilitator family. Here we demonstrate that MamB and MamM are multifunctional proteins involved in several steps of magnetosome formation. Whereas both proteins were essential for magnetite biomineralization, only deletion of mamB resulted in loss of magnetosome membrane vesicles. MamB stability depended on the p... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5331374 Tue, 18 Oct 2011 04:00:00 +0100 5331374 http://www.medworm.com/index.php?rid=5321921&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07852.x SummaryFounded on ground‐breaking discoveries such as the operon model by Jacob and Monod more than 50 years ago, molecular microbiology is now one of the most vibrant disciplines of the life sciences. The first Mol Micro Meeting Würzburg (“M3W") hosted more than 160 scientists from 14 countries to exchange their latest ideas in this field of research. Divided into the four main sessions Gene Regulation, Pathogenesis, Microbial Cell Biology and Signalling, the conference provided insight into current advances and future goals and challenges. (Source: Molecular Microbiology) Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5321921 Fri, 14 Oct 2011 04:00:00 +0100 5321921 http://www.medworm.com/index.php?rid=5321920&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07853.x In this report, we deciphered the regulatory role of CsrABb on FlaB synthesis and the mechanism involved by analyzing two mutants, csrABb‐ (a deletion mutant of csrABb) and csrABb+ (a mutant conditionally over‐expressing csrABb). We found that FlaB accumulation was significantly inhibited in csrABb+ but was substantially increased in csrABb‐. In contrast, the levels of other flagellar proteins remained unchanged. Cryo‐electron tomography and immuno‐fluorescence microscopic analyses revealed that the altered synthesis of CsrABb in these two mutants specifically affected flagellar filament length. The leader sequence of flaB transcript contains two conserved CsrA‐binding sites, with one of these sites overlapping the Shine‐Dalgarno sequence. We found that CsrABb bound to the fl... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5321920 Fri, 14 Oct 2011 04:00:00 +0100 5321920 http://www.medworm.com/index.php?rid=5321919&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07855.x SummaryResistance to quinoline antimalarial drugs has emerged in different parts of the world and involves sets of discrete mutational changes in pfcrt and pfmdr1 in the human malaria parasite Plasmodium falciparum. To better understand how the different polymorphic haplotypes of pfmdr1 and pfcrt contribute to drug resistance, we have conducted a linkage analysis in the F1 progeny of a genetic cross where we assess both the susceptibility and the amount of accumulation of chloroquine, amodiaquine, quinine and quinidine. Our data show that the different pfcrt and pfmdr1 haplotypes confer drug specific responses which, depending on the drug, may affect drug accumulation or susceptibility or both. These findings suggest that PfCRT and PfMDR1 are carriers of antimalarial drugs, but that the in... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5321919 Fri, 14 Oct 2011 04:00:00 +0100 5321919 http://www.medworm.com/index.php?rid=5321918&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07861.x SummaryArchaea, like bacteria and eukaryotes contain proteins involved in various mechanisms of DNA repair, highlighting the importance of these processes for all forms of life. Species of the order Sulfolobales of hyperthermophilic crenarchaeota are equipped with a strongly UV‐inducible type IV pilus system that promotes cellular aggregation. Here we demonstrate by fluorescence in situ hybridization that cellular aggregates are formed based on a species‐specific recognition process and that UV‐induced cellular aggregation mediates chromosomal marker exchange with high frequency. Recombination rates exceeded those of uninduced cultures by up to three orders of magnitude. Knockout strains of S. acidocaldarius incapable of pilus production could not self‐aggregate, but were partners ... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5321918 Fri, 14 Oct 2011 04:00:00 +0100 5321918 http://www.medworm.com/index.php?rid=5311522&cid=s_32053_77_f&fid=32053&url=http%3A%2F%2Fdx.doi.org%2F10.1111%252Fj.1365-2958.2011.07851.x SummaryMicroorganisms are invariably exposed to abrupt changes in their environment, and consequently display robust, high plasticity gene programmes to respond to stresses. In fission yeast, the Sty1 pathway is activated in response to diverse stress conditions, such as osmotic and oxidative stress, heat shock or nitrogen deprivation. The MAP kinase Sty1 and its substrate, the transcription factor Atf1, regulate diverse processes mainly at the nucleus. For instance, Sty1, Atf1 and its heterodimeric partner Pcr1 participate in promoting recombination at some hot spots, and in the assembly of heterochromatin at the mating locus. Their main role, however, is to engage a wide gene expression programme aimed to allow cellular survival by decreasing and repairing the damage exerted. Once Sty1 a... Molecular Microbiology journals http://www.medworm.com/rss/comments.php?id=5311522 Thu, 13 Oct 2011 04:00:00 +0100 5311522