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Competitive activation of the Escherichia coli argO gene coding for an arginine exporter by the transcriptional regulators Lrp and ArgPEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In vivo and in vitro analyses indicate that transcription of the argO gene coding for an arginine exporter is regulated by the global transcriptional regulator Lrp, an effect that went by unnoticed in previous genome-scale screenings of the Lrp regulatory network in Escherichia coli. Lrp activates the argO promoter fourfold; exogenous leucine antagonizes, but does not completely eliminate this effect. Activation by Lrp interferes with the previously demonstrated activation of the argO promoter by ArgP. This interference results from the mutual inhibitory binding of the two activators to overlapping targets. As a consequenc...
Source: Molecular Microbiology - November 20, 2009 Category: Microbiology Authors: Eveline Peeters, Phu Nguyen Le Minh, Maria Foulquié-Moreno, Daniel Charlier Source Type: journals

Rapid cleavage of RNA by RNase E in the absence of 5' monophosphate stimulationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The best characterized pathway for the initiation of mRNA degradation in Escherichia coli involves the removal of the 5'-terminal pyrophosphate to generate a monophosphate group that stimulates endonucleolytic cleavage by RNase E. We show here however, using well-characterized oligonucleotide substrates and mRNA transcripts, that RNase E can cleave certain RNAs rapidly without requiring a 5'-monophosphorylated end. Moreover, the minimum substrate requirement for this mode of cleavage, which can be categorized as 'direct' or 'internal' entry, appears to be multiple single-stranded segments in a conformational context that a...
Source: Molecular Microbiology - November 19, 2009 Category: Microbiology Authors: Louise Kime, Stefanie S. Jourdan, Jonathan A. Stead, Ana Hidalgo-Sastre, Kenneth J. McDowall Source Type: journals

Expression of the yeast aquaporin Aqy2 affects cell surface properties under the control of osmoregulatory and morphogenic signalling pathwaysEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Aquaporins mediate rapid and selective water transport across biological membranes. The yeast Saccharomyces cerevisiae possesses two aquaporins, Aqy1 and Aqy2. Here, we show that Aqy2 is involved in controlling cell surface properties and that its expression is controlled by osmoregulatory and morphogenic signalling pathways. Deletion of AQY2 results in diminished fluffy colony morphology while overexpression of AQY2 causes strong agar invasion and adherence to plastic surfaces. Hyper-osmotic stress inhibits morphological developments including the above characteristics as well as AQY2 expression through the osmoregulatory...
Source: Molecular Microbiology - November 14, 2009 Category: Microbiology Authors: Kentaro Furukawa, Frédéric Sidoux-Walter, Stefan Hohmann Source Type: journals

Mutation of CRE1 in Fusarium oxysporum reverts the pathogenicity defects of the FRP1 deletion mutantEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The F-box protein Frp1 is required for pathogenicity of Fusarium oxysporum f. sp. lycopersici towards tomato. The [Delta]frp1 mutant is deficient in expression of genes for cell wall-degrading enzymes (CWDEs) and ICL1, encoding a key enzyme for the assimilation of C2 carbon sources. An explanation for the inability of the [Delta]frp1 mutant to express these genes may be found in constitutive carbon catabolite repression. Cre1 is the transcriptional repressor in filamentous fungi known to repress several CWDE genes and other genes required for assimilation of non-sugar carbon sources. Here, we demonstrate that Frp1 and Cre1...
Source: Molecular Microbiology - November 13, 2009 Category: Microbiology Authors: Wilfried Jonkers, Martijn Rep Source Type: journals

Co-evolution of multipartite interactions between an extended tmRNA tag and a robust Lon protease in MycoplasmaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Messenger RNAs that lack in-frame stop codons promote ribosome stalling and accumulation of aberrant and potentially harmful polypeptides. The SmpB-tmRNA quality control system has evolved to solve problems associated with non-stop mRNAs, by rescuing stalled ribosomes and directing the addition of a peptide tag to the C-termini of the associated proteins, marking them for proteolysis. In Escherichia coli, the ClpXP system is the major contributor to disposal of tmRNA-tagged proteins. We have shown that the AAA+ Lon protease can also degrade tmRNA-tagged proteins, but with much lower efficiency. Here, we present a unique ca...
Source: Molecular Microbiology - November 13, 2009 Category: Microbiology Authors: Zhiyun Ge, A. Wali Karzai Source Type: journals

Novel Sinorhizobium meliloti quorum sensing positive and negative regulatory feedback mechanisms respond to phosphate availabilityEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study, we have characterized novel mechanisms of transcription control through which the system regulates itself. At low AHL levels a positive feedback loop activates expression of sinI (AHL synthase), resulting in amplification of AHL levels. At high AHL levels, expression of sinI is reduced by a negative feedback loop. These feedback mechanisms are mediated by the LuxR-type regulators ExpR and SinR. Expression of sinR and expR is regulated by ExpR in the presence of AHLs. A novel ExpR binding site in the promoter of sinR is responsible for the reduction of expression of this gene. In addition, expression of sinR,...
Source: Molecular Microbiology - November 12, 2009 Category: Microbiology Authors: Matthew McIntosh, Stefan Meyer, Anke Becker Source Type: journals

The role of absC, a novel regulatory gene for secondary metabolism, in zinc-dependent antibiotic production in Streptomyces coelicolor A3(2)Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The availability of zinc was shown to have a marked influence on the biosynthesis of actinorhodin in Streptomyces coelicolor A3(2). Production of actinorhodin and undecylprodigiosin was abolished when a novel pleiotropic regulatory gene, absC, was deleted, but only when zinc concentrations were low. AbsC was shown to control expression of the gene cluster encoding production of coelibactin, an uncharacterized non-ribosomally synthesized peptide with predicted siderophore-like activity, and the observed defect in antibiotic production was found to result from elevated expression of this gene cluster. Promoter regions in the...
Source: Molecular Microbiology - November 10, 2009 Category: Microbiology Authors: Andy Hesketh, Holger Kock, Saraspadee Mootien, Mervyn Bibb Source Type: journals

Cytochrome P450 125 (CYP125) catalyses C26-hydroxylation to initiate sterol side-chain degradation in Rhodococcus jostii RHA1Email this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The cyp125 gene of Rhodococcus jostii RHA1 was previously found to be highly upregulated during growth on cholesterol and the orthologue in Mycobacterium tuberculosis (rv3545c) has been implicated in pathogenesis. Here we show that cyp125 is essential for R. jostii RHA1 to grow on 3-hydroxysterols such as cholesterol, but not on 3-oxo sterol derivatives, and that CYP125 performs an obligate first step in cholesterol degradation. The involvement of cyp125 in sterol side-chain degradation was confirmed by disrupting the homologous gene in Rhodococcus rhodochrous RG32, a strain that selectively degrades the cholesterol side-c...
Source: Molecular Microbiology - November 10, 2009 Category: Microbiology Authors: Kamila Z. Rosłoniec, Maarten H. Wilbrink, Jenna K. Capyk, William W. Mohn, Martin Ostendorf, Robert van der Geize, Lubbert Dijkhuizen, Lindsay D. Eltis Source Type: journals

Differential substrate specificity of group I and group II chaperonins in the archaeon Methanosarcina mazeiEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Chaperonins are macromolecular machines that assist in protein folding. The archaeon Methanosarcina mazei has acquired numerous bacterial genes by horizontal gene transfer. As a result, both the bacterial group I chaperonin, GroEL, and the archaeal group II chaperonin, thermosome, coexist. A proteome-wide analysis of chaperonin interactors was performed to determine the differential substrate specificity of GroEL and thermosome. At least 13% of soluble M. mazei proteins interact with chaperonins, with the two systems having partially overlapping substrate sets. Remarkably, chaperonin selectivity is independent of phylogene...
Source: Molecular Microbiology - November 7, 2009 Category: Microbiology Authors: Angela M. Hirtreiter, Giulia Calloni, Francesca Forner, Burghardt Scheibe, Magda Puype, Joel Vandekerckhove, Matthias Mann, F. Ulrich Hartl, Manajit Hayer-Hartl Source Type: journals

Pyoverdine and PQS mediated subpopulation interactions involved in Pseudomonas aeruginosa biofilm formationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Using flow chamber-grown Pseudomonas aeruginosa biofilms as model system, we show in the present study that formation of heterogeneous biofilms may occur through mechanisms that involve complex subpopulation interactions. One example of this phenomenon is expression of the iron-siderophore pyoverdine in one subpopulation being necessary for development of another subpopulation that does not itself express the pyoverdine synthesis genes. Another example is quorum sensing-controlled DNA release in one subpopulation being necessary for development of another subpopulation that does not itself express the quorum-sensing genes....
Source: Molecular Microbiology - November 2, 2009 Category: Microbiology Authors: Liang Yang, Martin Nilsson, Morten Gjermansen, Michael Givskov, Tim Tolker-Nielsen Source Type: journals

The antifungal protein PAF interferes with PKC/MPK and cAMP/PKA signalling of Aspergillus nidulansEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We report here that two signalling cascades are implicated in its antifungal activity. PAF activates the cAMP/protein kinase A (Pka) signalling cascade. A pkaA deletion mutant exhibited reduced sensitivity towards PAF. This was substantiated by the use of pharmacological modulators: PAF aggravated the effect of the activator 8-Br-cAMP and partially relieved the repressive activity of caffeine. Furthermore, the Pkc/mitogen-activated protein kinase (Mpk) signalling cascade mediated basal resistance to PAF, which was independent of the small GTPase RhoA. Non-functional mutations of both genes resulted in hypersensitivity towa...
Source: Molecular Microbiology - November 2, 2009 Category: Microbiology Authors: Ulrike Binder, Christoph Oberparleiter, Vera Meyer, Florentine Marx Source Type: journals

LrhA positively controls the expression of the locus of enterocyte effacement genes in enterohemorrhagic Escherichia coli by differential regulation of their master regulators PchA and PchBEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Genes essential for eliciting pathogenicity of enterohemorrhagic Escherichia coli are located within the locus of enterocyte effacement (LEE). Expression of LEE genes is positively regulated by paralogues PchA, PchB and PchC, which are encoded by separate loci of the chromosome. To elucidate the underlying regulatory mechanism, we screened transposon mutants exhibiting reduced expression of pchA, transcription level of which is highest among the pch genes. Here, we report that the LysR-homologue A (LrhA) positively regulated the transcription of pchA and pchB. A deletion in lrhA reduced the transcription levels of pchA and...
Source: Molecular Microbiology - November 2, 2009 Category: Microbiology Authors: Naoko Honda, Sunao Iyoda, Shouji Yamamoto, Jun Terajima, Haruo Watanabe Source Type: journals

DksA and ppGpp directly regulate transcription of the Escherichia coli flagellar cascadeEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We report here that the activities of promoters at all three levels of the cascade are much higher in strains lacking dksA, resulting in overproduction of flagellin and hyperflagellated cells. In vitro, DksA/ppGpp inhibits the flhDC promoter and the [sigma]70-dependent fliA promoter transcribing the gene for [sigma]28. However, DksA and ppGpp do not affect the [sigma]28-dependent fliA promoter or the [sigma]28-dependent fliC promoter in vitro, suggesting that the dramatic effects on expression of those genes in vivo are mediated indirectly through direct effects of DksA/ppGpp on FlhDC and [sigma]28 expression. We conclude ...
Source: Molecular Microbiology - November 2, 2009 Category: Microbiology Authors: Justin J. Lemke, Tim Durfee, Richard L. Gourse Source Type: journals

Roles of the extreme N-terminal region of FliH for efficient localization of the FliH–FliI complex to the bacterial flagellar type III export apparatusEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Most bacterial flagellar proteins are exported by the flagellar type III protein export apparatus for their self-assembly. FliI ATPase forms a complex with its regulator FliH and facilitates initial entry of export substrates to the export gate composed of six integral membrane proteins. The FliH[ndash]FliI complex also binds to the C ring of the basal body through a FliH[ndash]FliN interaction for efficient export. However, it remains unclear how these reactions proceed within the cell. Here, we analysed subcellular localization of FliI[ndash]YFP by fluorescence microscopy. FliI[ndash]YFP was localized to the flagellar ba...
Source: Molecular Microbiology - November 2, 2009 Category: Microbiology Authors: Tohru Minamino, Shinsuke D. J. Yoshimura, Yusuke V. Morimoto, Bertha González-Pedrajo, Nobunori Kami-ike, Keiichi Namba Source Type: journals

BosR (BB0647) governs virulence expression in Borrelia burgdorferiEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
This study thus not only has elucidated another key virulence gene of Bb, but also provides new insights into a previously unknown layer of gene regulation governing RpoS in Bb. (Source: Molecular Microbiology)
Source: Molecular Microbiology - November 2, 2009 Category: Microbiology Authors: Zhiming Ouyang, Manish Kumar, Toru Kariu, Shayma Haq, Martin Goldberg, Utpal Pal, Michael V. Norgard Source Type: journals

A PhoQ/P-regulated small RNA regulates sensitivity of Escherichia coli to antimicrobial peptidesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Non-coding small RNAs (sRNAs) play a major role in post-transcriptional regulation of gene expression. Of the 80 sRNAs that have been identified in E. coli, one-third bind to the RNA chaperone Hfq. Hfq both stabilizes these sRNAs in vivo and stimulates pairing to targets in vitro. A novel Hfq-dependent RNA, called here MgrR, was identified by its ability to bind Hfq. Expression of MgrR requires the PhoQ/PhoP two-component system; the PhoP response regulator is active under low Mg2+ concentrations and is an important virulence regulator in Salmonella; mgrR is also found in Salmonella species. Negatively regulated targets of...
Source: Molecular Microbiology - November 2, 2009 Category: Microbiology Authors: Kyung Moon, Susan Gottesman Source Type: journals

DNA relaxation-dependent phase biasing of the fim genetic switch in Escherichia coli depends on the interplay of H-NS, IHF and LRPEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Reversible inversion of the DNA element fimS is responsible for the phase variable expression of type 1 fimbriae in Escherichia coli. The FimB tyrosine integrase site-specific recombinase inverts fimS in the on-to-off and off-to-on directions with approximately equal efficiencies. However, when DNA supercoiling is relaxed, fimS adopts predominantly the on orientation. This orientational bias is known to require binding of the nucleoid-associated protein LRP within fimS. Here we show that binding of the IHF protein to a site immediately adjacent to fimS is also required for phase-on orientational bias. In the absence of bot...
Source: Molecular Microbiology - November 2, 2009 Category: Microbiology Authors: Colin P. Corcoran, Charles J. Dorman Source Type: journals

The cobinamide amidohydrolase (cobyric acid-forming) CbiZ enzyme: a critical activity of the cobamide remodelling system of Rhodobacter sphaeroidesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The chemical structures of cobamides [cobalamin (Cbl)-like compounds] are the same, except for the lower ligand, which in adenosylcobalamin (AdoCbl) is 5,6-dimethylbenzimidazole, and in adenosylpseudocobalamin (AdopseudoCbl) is adenine. Why the lower ligand of cobamides varies and what the mechanism of lower ligand replacement is are long-standing questions in the field of B12 biosynthesis. Work reported here uncovers the strategy used by the photosynthetic [alpha]-proteobacterium Rhodobacter sphaeroides to procure the cobamide it needs to grow on acetate as a carbon and energy source. On the basis of genetic and biochemic...
Source: Molecular Microbiology - November 2, 2009 Category: Microbiology Authors: Michael J. Gray, Jorge C. Escalante-Semerena Source Type: journals

Different roles for anti-sigma factors in siderophore signalling pathways of Pseudomonas aeruginosaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Group IV (extracytoplasmic function) sigma factors direct the expression of a large number of regulons in bacteria. The activities of many Group IV sigma factors are inhibited by members of a family of anti-sigma factor proteins, with appropriate environmental signals causing the sigma factor to be released for interaction with core RNA polymerase and consequent transcription of target genes. One subgroup of Group IV sigmas directs expression of genes for uptake of siderophores (iron-chelating compounds) by Gram-negative bacteria. The activities of these sigma factors are controlled by anti-sigma factors that span the cyto...
Source: Molecular Microbiology - November 2, 2009 Category: Microbiology Authors: Karla A. Mettrick, Iain L. Lamont Source Type: journals

A cryptochrome-like protein is involved in the regulation of photosynthesis genes in Rhodobacter sphaeroidesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Blue light receptors belonging to the cryptochrome/photolyase family are found in all kingdoms of life. The functions of photolyases in repair of UV-damaged DNA as well as of cryptochromes in the light-dependent regulation of photomorphogenetic processes and in the circadian clock in plants and animals are well analysed. In prokaryotes, the only role of members of this protein family that could be demonstrated is DNA repair. Recently, we identified a gene for a cryptochrome-like protein (CryB) in the [alpha]-proteobacterium Rhodobacter sphaeroides. The protein lacks the typical C-terminal extension of cryptochromes, and is...
Source: Molecular Microbiology - October 29, 2009 Category: Microbiology Authors: Anne-Kathrin Hendrischk, Sebastian Walter Frühwirth, Julia Moldt, Richard Pokorny, Sebastian Metz, Gebhard Kaiser, Andreas Jäger, Alfred Batschauer, Gabriele Klug Source Type: journals

Dual control by perfectly overlapping σ54- and σ70-promoters adjusts small RNA GlmY expression to different environmental signalsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In Escherichia coli synthesis of glucosamine-6-phosphate synthase GlmS is feedback-controlled by a regulatory cascade composed of small RNAs GlmY and GlmZ. When GlcN6P becomes limiting, GlmY accumulates and inhibits processing of GlmZ. Full-length GlmZ base-pairs with the glmS transcript and activates synthesis of GlmS, which re-synthesizes GlcN6P. Here we show that glmY expression is controlled by two overlapping promoters with the same transcription start site. A [sigma]70-dependent promoter contributes to glmY transcription during exponential growth. Alternatively, glmY can be transcribed from a [sigma]54-dependent prom...
Source: Molecular Microbiology - October 29, 2009 Category: Microbiology Authors: Birte Reichenbach, Yvonne Göpel, Boris Görke Source Type: journals

Lateral FtsZ association and the assembly of the cytokinetic Z ring in bacteriaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Cell division in bacteria is facilitated by a polymeric ring structure, the Z ring, composed of tubulin-like FtsZ protofilaments. Recently it has been shown that in Bacillus subtilis, the Z ring forms through the cell cycle-mediated remodelling of a helical FtsZ polymer. To investigate how this occurs in vivo, we have exploited a unique temperature-sensitive strain of B. subtilis expressing the mutant protein FtsZ(Ts1). FtsZ(Ts1) is unable to complete Z ring assembly at 49°C, becoming trapped at an intermediate stage in the helix-to-ring progression. To determine why this is the case, we used a combination of methods to i...
Source: Molecular Microbiology - October 27, 2009 Category: Microbiology Authors: Leigh G. Monahan, Andrew Robinson, Elizabeth J. Harry Source Type: journals

Identification and characterization of three novel EsaI/EsaR quorum-sensing controlled stewartan exopolysaccharide biosynthetic genes in Pantoea stewartii ssp. stewartiiEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
(Source: Molecular Microbiology)
Source: Molecular Microbiology - October 23, 2009 Category: Microbiology Authors: Aurélien Carlier, Lindsey Burbank, Susanne B. von Bodman Source Type: journals

Reconstructing the evolutionary history of nitrotoluene detection in the transcriptional regulator NtdREmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Many toxic man-made compounds have been introduced into the environment, and bacterial strains that are able to grow on them are ideal model systems for studying the evolution of metabolic pathways and regulatory systems. Acidovorax sp. strain JS42 is unique in its ability to use 2-nitrotoluene as a sole carbon, nitrogen, and energy source for growth. The LysR-type transcriptional regulator NtdR activates expression of the 2-nitrotoluene degradation genes not only when nitroaromatic compounds are present, but also in the presence of a wide range of aromatic acids and analogues. The molecular determinants of inducer specifi...
Source: Molecular Microbiology - October 21, 2009 Category: Microbiology Authors: Kou-San Ju, Juanito V. Parales, Rebecca E. Parales Source Type: journals

The γ-glutamylcysteine synthetase gene of Leishmania is essential and involved in response to oxidantsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Gamma-glutamylcysteine synthetase, encoded by the GSH1 gene, is the rate-limiting enzyme in the biosynthesis of glutathione and of trypanothione in Leishmania. The importance of GSH1 was assessed by generating GSH1 null mutants in Leishmania infantum. Removal of even a single wild-type allelic copy of GSH1 invariably led to the generation of an extra copy of GSH1, maintaining two intact wild-type alleles. However, by first supplementing the parasites with a rescue plasmid, we succeeded in obtaining both a single and null chromosomal GSH1 mutants. Parasites with one intact GSH1 chromosomal allele lost the rescuing plasmid b...
Source: Molecular Microbiology - October 21, 2009 Category: Microbiology Authors: Angana Mukherjee, Gaétan Roy, Chantal Guimond, Marc Ouellette Source Type: journals

Role of Escherichia coli DNA polymerase I in chromosomal DNA replication fidelityEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We have investigated the possible role of Escherichia coli DNA polymerase (Pol) I in chromosomal replication fidelity. This was done by substituting the chromosomal polA gene by the polAexo variant containing an inactivated 3'[rarr]5' exonuclease, which serves as a proofreader for this enzyme's misinsertion errors. Using this strain, activities of Pol I during DNA replication might be detectable as increases in the bacterial mutation rate. Using a series of defined lacZ reversion alleles in two orientations on the chromosome as markers for mutagenesis, 1.5- to 4-fold increases in mutant frequencies were observed. In genera...
Source: Molecular Microbiology - October 19, 2009 Category: Microbiology Authors: Karolina Makiela-Dzbenska, Malgorzata Jaszczur, Magdalena Banach-Orlowska, Piotr Jonczyk, Roel M. Schaaper, Iwona J. Fijalkowska Source Type: journals

Null mutations in Sinorhizobium meliloti exoS and chvI demonstrate the importance of this two-component regulatory system for symbiosisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We present evidence that the S. meliloti ExoS/ChvI two-component regulatory system is essential for symbiosis with alfalfa. Phenotypic analyses of exoS and chvI null mutant strains demonstrate that ExoS/ChvI controls both succinoglycan and galactoglucan production and is required for growth on over 21 different carbon sources. These new findings suggest that the ExoS/ChvI regulatory targets might not be the exo genes that are specific for succinoglycan biosynthesis but rather genes that have common influence on both succinoglycan and galactoglucan production. Other studied alpha-proteobacteria ExoS/ChvI orthologues are req...
Source: Molecular Microbiology - October 19, 2009 Category: Microbiology Authors: Louise Bélanger, Kristin A. Dimmick, Jacquelyn S. Fleming, Trevor C. Charles Source Type: journals

Polyphosphate kinase 2: a modulator of nucleoside diphosphate kinase activity in mycobacteriaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We report that recombinant PPK2 of Mycobacterium tuberculosis catalyses the synthesis of GTP from GDP using polyphosphate rather than ATP as phosphate donor. Unlike that of PPK1, this is the favoured reaction of PPK2. The sites of autophosphorylation, H115 and H247, as well as G74 were critical for GTP-synthesizing activity. Compromised survival of a ppk2 knockout (PPK2-KO) of Mycobacterium smegmatis under heat or acid stress or hypoxia, and the ability of ppk2 of M. tuberculosis to complement this, confirmed that PPK2 plays a role in mycobacterial survival under stress. Intracellular ATP : GTP ratio was higher in PPK2-KO ...
Source: Molecular Microbiology - October 19, 2009 Category: Microbiology Authors: Kamakshi Sureka, Sourav Sanyal, Joyoti Basu, Manikuntala Kundu Source Type: journals

Evidence that a secondary metabolic biosynthetic gene cluster has grown by gene relocation during evolution of the filamentous fungus FusariumEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Trichothecenes are terpene-derived secondary metabolites produced by multiple genera of filamentous fungi, including many plant pathogenic species of Fusarium. These metabolites are of interest because they are toxic to animals and plants and can contribute to pathogenesis of Fusarium on some crop species. Fusarium graminearum and F. sporotrichioides have trichothecene biosynthetic genes (TRI) at three loci: a 12-gene TRI cluster and two smaller TRI loci that consist of one or two genes. Here, comparisons of additional Fusarium species have provided evidence that TRI loci have a complex evolutionary history that has includ...
Source: Molecular Microbiology - October 19, 2009 Category: Microbiology Authors: Robert H. Proctor, Susan P. McCormick, Nancy J. Alexander, Anne E. Desjardins Source Type: journals

The H-NS-like protein StpA represses the RpoS (σ38) regulon during exponential growth of Salmonella TyphimuriumEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
StpA is a paralogue of the nucleoid-associated protein H-NS that is conserved in a range of enteric bacteria and had no known function in Salmonella Typhimurium. We show that 5% of the Salmonella genome is regulated by StpA, which contrasts with the situation in Escherichia coli where deletion of stpA only had minor effects on gene expression. The StpA-dependent genes of S. Typhimurium are a specific subset of the H-NS regulon that are predominantly under the positive control of [sigma]38 (RpoS), CRP-cAMP and PhoP. Regulation by StpA varied with growth phase; StpA controlled [sigma]38 levels at mid-exponential phase by pre...
Source: Molecular Microbiology - October 19, 2009 Category: Microbiology Authors: Sacha Lucchini, Paul McDermott, Arthur Thompson, Jay C.D. Hinton Source Type: journals

High-resolution architecture of the outer membrane of the Gram-negative bacteria Roseobacter denitrificansEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The outer membrane of Gram-negative bacteria protects the cell against bactericidal substances. Passage of nutrients and waste is assured by outer membrane porins, beta-barrel transmembrane channels. While atomic structures of several porins have been solved, so far little is known on the supramolecular structure of the outer membrane. Here we present the first high-resolution view of a bacterial outer membrane gently purified maintaining remnants of peptidoglycan on the perisplasmic surface. Atomic force microscope images of outer membrane fragments of the size of [sim]50% of the bacterial envelope revealed that outer mem...
Source: Molecular Microbiology - October 15, 2009 Category: Microbiology Authors: Szymon Jarosławski, Katia Duquesne, James N. Sturgis, Simon Scheuring Source Type: journals

Functional stratification of the Spitzenkörper of Neurospora crassaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
GS-1 (ncu04189) is a protein required for the synthesis of [beta]-1,3-glucan in Neurospora crassa. As chitin, [beta]-1,3-glucan is a morphogenetically relevant component of the fungal cell wall. Previously, we showed that chitin synthases are delivered to the growing hyphal tip of N. crassa by secretory microvesicles that follow an unconventional route and accumulate in the core of the Spitzenkörper (Spk). Tagged with the green fluorescent protein (GFP), GS-1 accumulated in the hyphal apex forming a dynamic and pleomorphic ring-like structure ('Spitzenring') that corresponded to the Spk outer macrovesicular stratum and su...
Source: Molecular Microbiology - October 15, 2009 Category: Microbiology Authors: Jorge Verdín, Salomon Bartnicki-Garcia, Meritxell Riquelme Source Type: journals

Activation of σ28-dependent transcription in Escherichia coli by the cyclic AMP receptor protein requires an unusual promoter organizationEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
We report that the ternary activator[ndash]RNA polymerase[ndash]aer promoter open complex is organized differently from complexes at previously characterized promoters. Among other E. coli promoters recognized by RNA polymerase containing [sigma]28, only the trg promoter is activated directly by the cyclic AMP receptor protein. The organization of the different promoter elements and the activator binding site at the trg promoter is the same as at the aer promoter, suggesting a common activation mechanism. (Source: Molecular Microbiology)
Source: Molecular Microbiology - October 15, 2009 Category: Microbiology Authors: Kerry Hollands, David J. Lee, Georgina S. Lloyd, Stephen J. W. Busby Source Type: journals

Distinct β-clamp interactions govern the activities of the Y family PolIV DNA polymeraseEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The prototypic Y family DNA polymerase IV (PolIV) of Escherichia coli is involved in multiple replication-associated processes including spontaneous mutagenesis, translesion synthesis (TLS), cell fitness, survival under stressful conditions and checkpoint like functions. It interacts physically and functionally with the replisome's [beta] processivity clamp through the canonical PolIV C-terminal peptide (CTP). A second interaction that involves a portion of the little finger (LF) domain of PolIV has been structurally described. Here we show that the LF[ndash][beta] interaction stabilizes the clamp[ndash]polymerase complex ...
Source: Molecular Microbiology - October 15, 2009 Category: Microbiology Authors: Jérôme Wagner, Hélène Etienne, Robert P. Fuchs, Agnes Cordonnier, Dominique Burnouf Source Type: journals

Direct activator/co-activator interaction is essential for bacteriophage T4 middle gene expressionEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The bacteriophage T4 AsiA protein is a bifunctional regulator that inhibits transcription from the major class of bacterial promoters and also serves as an essential co-activator of transcription from T4 middle promoters. AsiA binds the primary [sigma] factor in Escherichia coli, [sigma]70, and modifies the promoter recognition properties of the [sigma]70-containing RNA polymerase (RNAP) holoenzyme. In its role as co-activator, AsiA directs RNAP to T4 middle promoters in the presence of the T4-encoded activator MotA. According to the current model for T4 middle promoter activation, AsiA plays an indirect role in stabilizin...
Source: Molecular Microbiology - October 15, 2009 Category: Microbiology Authors: Andy H. Yuan, Ann Hochschild Source Type: journals

Molybdenum and tungsten in Campylobacter jejuni: their physiological role and identification of separate transporters regulated by a single ModE-like proteinEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Campylobacter jejuni is an important human pathogen that causes millions of cases of food-borne enteritis each year. The C. jejuni respiratory chain is highly branched and contains at least four enzymes predicted to contain a metal binding pterin (MPT), with the metal being either molybdenum or tungsten. Also predicted are two separate transport systems, one for molybdenum encoded by modABC and a second for tungsten encoded by tupABC. Both transport systems were mutated and the activities of the four predicted MPT-containing enzymes were assayed in the presence of molybdenum and tungsten in wild-type and mod and tup backgr...
Source: Molecular Microbiology - October 14, 2009 Category: Microbiology Authors: Michael E. Taveirne, Michael L. Sikes, Jonathan W. Olson Source Type: journals

Cryptococcus neoformans Site-2 protease is required for virulence and survival in the presence of azole drugsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
In this study, we characterize the C. neoformans serotype A Sre1 and its activating protease, Stp1. We demonstrate that Stp1 is a functionally conserved orthologue of the mammalian Site-2 protease and that Stp1 cleaves Sre1 within its predicted first transmembrane segment. Gene expression analysis revealed that Stp1 is required for both Sre1-dependent and Sre1-independent gene transcription, indicating that other substrates of Stp1 may exist. Using gas chromatography, we showed that Sre1 and Stp1 are required for both normoxic and hypoxic ergosterol biosynthesis, and therefore cells lacking SRE1 or STP1 are defective for g...
Source: Molecular Microbiology - October 13, 2009 Category: Microbiology Authors: Clara M. Bien, Yun C. Chang, W. David Nes, Kyung J. Kwon-Chung, Peter J. Espenshade Source Type: journals

A role for tungsten in the biology of Campylobacter jejuni: tungstate stimulates formate dehydrogenase activity and is transported via an ultra-high affinity ABC system distinct from the molybdate transporterEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The food-borne pathogen Campylobacter jejuni possesses no known tungstoenzymes, yet encodes two ABC transporters (Cj0300[ndash]0303 and Cj1538[ndash]1540) homologous to bacterial molybdate (ModABC) uptake systems and the tungstate transporter (TupABC) of Eubacterium acidaminophilum respectively. The actual substrates and physiological role of these transporters were investigated. Tryptophan fluorescence spectroscopy and isothermal titration calorimetry of the purified periplasmic binding proteins of each system revealed that while Cj0303 is unable to discriminate between molybdate and tungstate (KD values for both ligands ...
Source: Molecular Microbiology - October 12, 2009 Category: Microbiology Authors: Jonathan P. Smart, Matthew J. Cliff, David J. Kelly Source Type: journals

SpoIIIE and a novel type of DNA translocase, SftA, couple chromosome segregation with cell division in Bacillus subtilisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Cell division must only occur once daughter chromosomes have been fully separated. However, the initiating event of bacterial cell division, assembly of the FtsZ ring, occurs while chromosome segregation is still ongoing. We show that a two-step DNA translocase system exists in Bacillus subtilis that couples chromosome segregation and cell division. The membrane-bound DNA translocase SpoIIIE assembled very late at the division septum, and only upon entrapment of DNA, while its orthologue, SftA (YtpST), assembled at each septum in B. subtilis soon after FtsZ. Lack of SftA resulted in a moderate segregation defect at a late ...
Source: Molecular Microbiology - October 8, 2009 Category: Microbiology Authors: Christine Kaimer, José Eduardo González-Pastor, Peter L. Graumann Source Type: journals

Replication fork collisions cause pathological chromosomal amplification in cells lacking RecG DNA translocaseEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Duplication and transmission of chromosomes require precise control of chromosome replication and segregation. Here we present evidence that RecG is a major factor influencing these processes in bacteria. We show that the extensive DnaA-independent stable DNA replication observed without RecG can lead to replication of any area of the chromosome. This replication is further elevated following irradiation with UV light and appears to be perpetuated by secondary events that continue long after the elimination of UV lesions. The resulting pathological cascade is associated with an increased number of replication forks travers...
Source: Molecular Microbiology - October 8, 2009 Category: Microbiology Authors: Christian J. Rudolph, Amy L. Upton, Robert G. Lloyd Source Type: journals

Listeria monocytogenes CtaP is a multifunctional cysteine transport-associated protein required for bacterial pathogenesisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The bacterial pathogen Listeria monocytogenes survives under a myriad of conditions in the outside environment and within the human host where infections can result in severe disease. Bacterial life within the host requires the expression of genes with roles in nutrient acquisition as well as the biosynthesis of bacterial products required to support intracellular growth. A gene product identified as the substrate-binding component of a novel oligopeptide transport system (encoded by lmo0135) was recently shown to be required for L. monocytogenes virulence. Here we demonstrate that lmo0135 encodes a multifunctional protein...
Source: Molecular Microbiology - October 8, 2009 Category: Microbiology Authors: Bobbi Xayarath, Hélène Marquis, Gary C. Port, Nancy E. Freitag Source Type: journals

Cell elongation and branching are regulated by differential phosphorylation states of the nuclear Dbf2-related kinase COT1 in Neurospora crassaEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Dysfunction of the Neurospora crassa nuclear Dbf2-related kinase COT1 leads to cessation of tip extension and massive induction of new sites of growth. To determine the role phosphorylation plays in COT1 function, we mutated COT1 residues corresponding to positions of highly conserved nuclear Dbf2-related phosphorylation sites. Analyses of the point-mutation cot-1 strains (mimicking non- and constitutively phosphorylated states) indicate the involvement of COT1 phosphorylation in the regulation of hyphal elongation and branching as well as asexual development by altering cell wall integrity and actin organization. Phosphor...
Source: Molecular Microbiology - October 8, 2009 Category: Microbiology Authors: Carmit Ziv, Galia Kra-Oz, Rena Gorovits, Sabine März, Stephan Seiler, Oded Yarden Source Type: journals

Degradation of nitroaromatic compounds: a model to study evolution of metabolic pathwaysEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Although many nitroaromatic compounds have been in nature for only a few decades, bacteria have already evolved the ability to metabolize them. Both horizontal transfer of genes and mutagenesis induced under stressful conditions might facilitate evolution of new catabolic pathways. Nitrotoluene degradation pathways are supposedly derived from an ancestral naphthalene degradation pathway. The 2-nitrotoluene degradation genes in Acidovorax sp. strain JS42 are controlled by the transcriptional activator NtdR, which differs from NagR, the activator of the naphthalene degradation operon in Ralstonia sp. strain U2, by only five ...
Source: Molecular Microbiology - October 7, 2009 Category: Microbiology Authors: Maia Kivisaar Source Type: journals

Streptococcus mutans autolysin AtlA is a fibronectin-binding protein and contributes to bacterial survival in the bloodstream and virulence for infective endocarditisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Streptococcus mutans, a commensal of the human oral cavity, can survive in the bloodstream and cause infective endocarditis (IE). However, the virulence factors associated with this manifestation of disease are not known. Here, we demonstrate that AtlA, an autolysin of S. mutans is a newly identified fibronectin (Fn) binding protein and contributes to bacterial resistance to phagocytosis and survival in the bloodstream. Interestingly, prior exposure to plasma at low concentrations was sufficient to enhance bacterial survival in the circulation. Calcium ions at physiological plasma concentrations induced maturation of AtlA ...
Source: Molecular Microbiology - October 7, 2009 Category: Microbiology Authors: Chiau-Jing Jung, Quan-Hau Zheng, Ya-Hsiung Shieh, Chi-Shuan Lin, Jean-San Chia Source Type: journals

An upstream activation element exerting differential transcriptional activation on an archaeal promoterEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Microorganisms can utilize different sugars as energy and carbon sources and the genes involved in sugar metabolism often exhibit highly regulated expression. To study cis-acting elements controlling arabinose-responsive expression in archaea, the promoter of the Sulfolobus solfataricus araS gene encoding an arabinose binding protein was characterized using an Sulfolobus islandicus reporter gene system. The minimal active araS promoter (ParaS) was found to be 59 nucleotides long and harboured four promoter elements: an ara-box, an upstream transcription factor B-responsive element (BRE), a TATA-box and a proximal promoter ...
Source: Molecular Microbiology - October 7, 2009 Category: Microbiology Authors: Nan Peng, Qiu Xia, Zhengjun Chen, Yun Xiang Liang, Qunxin She Source Type: journals

Bacterial chemoattraction towards jasmonate plays a role in the entry of Dickeya dadantii through wounded tissuesEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Jasmonate is a key signalling compound in plant defence that is synthesized in wounded tissues. In this work, we have found that this molecule is also a strong chemoattractant for the phythopathogenic bacteria Dickeya dadantii (ex-Erwinia chysanthemi). Jasmonic acid induced the expression of a subset of bacterial genes possibly involved in virulence/survival in the plant apoplast and bacterial cells pre-treated with jasmonate showed increased virulence in chicory and Saintpaulia leaves. We also showed that tissue wounding induced bacterial spread through the leaf surface. Moreover, the jasmonate-deficient aos1 Arabidopsis ...
Source: Molecular Microbiology - October 7, 2009 Category: Microbiology Authors: Maria Antunez-Lamas, Ezequiel Cabrera, Emilia Lopez-Solanilla, Roberto Solano, Pablo González-Melendi, Jose Manuel Chico, Ian Toth, Paul Birch, Leighton Prichard, Hui Liu, Pablo Rodriguez-Palenzuela Source Type: journals

An intricate network of regulators controls biofilm formation and colonization by Vibrio fischeriEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
The initial encounter between a microbe and its host can dictate the success of the interaction, be it symbiosis or pathogenesis. This is the case, for example, in the symbiosis between the bacterium Vibrio fischeri and the squid Euprymna scolopes, which proceeds via a biofilm-like bacterial aggregation, followed by entry and growth. A key regulator, the sensor kinase RscS, is critical for symbiotic biofilm formation and colonization. When introduced into a fish symbiont strain that naturally lacks the rscS gene and cannot colonize squid, RscS permits colonization, thereby extending the host range of these bacteria. RscS c...
Source: Molecular Microbiology - October 7, 2009 Category: Microbiology Authors: Karen L. Visick Source Type: journals

Role of the heat shock transcription factor, Hsf1, in a major fungal pathogen that is obligately associated with warm-blooded animalsEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
All organisms have evolved mechanisms that protect them against environmental stress. The major fungal pathogen of humans, Candida albicans, has evolved robust stress responses that protect it against human immune defences and promote its pathogenicity. However, C. albicans is unlikely to be exposed to heat shock as it is obligatorily associated with warm-blooded animals. Therefore, we examined the role of the heat shock transcription factor (Hsf1) in this pathogen. We show that C. albicans expresses an evolutionarily conserved Hsf1 (orf19.4775) that is phosphorylated in response to heat shock, induces transcription via th...
Source: Molecular Microbiology - October 7, 2009 Category: Microbiology Authors: Susan Nicholls, Michelle D. Leach, Claire L. Priest, Alistair J. P. Brown Source Type: journals

The β-lactam-sensitive d,d-carboxypeptidase activity of Pbp4 controls the l,d and d,d transpeptidation pathways in Corynebacterium jeikeiumEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Corynebacterium jeikeium is an emerging nosocomial pathogen responsible for vascular catheters infections, prosthetic endocarditis and septicemia. The treatment of C. jeikeium infections is complicated by the multiresistance of clinical isolates to antibiotics, in particular to [beta]-lactams, the most broadly used class of antibiotics. To gain insight into the mechanism of [beta]-lactam resistance, we have determined the structure of the peptidoglycan and shown that C. jeikeium has the dual capacity to catalyse formation of cross-links generated by transpeptidases of the d,d and l,d specificities. Two ampicillin-insensiti...
Source: Molecular Microbiology - October 5, 2009 Category: Microbiology Authors: Marie Lavollay, Michel Arthur, Martine Fourgeaud, Lionel Dubost, Arul Marie, Philippe Riegel, Laurent Gutmann, Jean-Luc Mainardi Source Type: journals

The coat morphogenetic protein SpoVID is necessary for spore encasement in Bacillus subtilisEmail this article to a colleague. Save this article to My Clippings. Discuss or comment on this article.
Endospores formed by Bacillus subtilis are encased in a tough protein shell known as the coat, which consists of at least 70 different proteins. We investigated the process of spore coat morphogenesis using a library of 40 coat proteins fused to green fluorescent protein and demonstrate that two successive steps can be distinguished in coat assembly. The first step, initial localization of proteins to the spore surface, is dependent on the coat morphogenetic proteins SpoIVA and SpoVM. The second step, spore encasement, requires a third protein, SpoVID. We show that in spoVID mutant cells, most coat proteins assembled into ...
Source: Molecular Microbiology - October 1, 2009 Category: Microbiology Authors: Katherine H. Wang, Anabela L. Isidro, Lia Domingues, Haig A. Eskandarian, Peter T. McKenney, Kevin Drew, Paul Grabowski, Ming-Hsiu Chua, Samantha N. Barry, Michelle Guan, Richard Bonneau, Adriano O. Henriques, Patrick Eichenberger Source Type: journals