scholarly journals Sigma B Contributes to PrfA-Mediated Virulence in Listeria monocytogenes

2002 ◽  
Vol 70 (7) ◽  
pp. 3948-3952 ◽  
Author(s):  
Celine A. Nadon ◽  
Barbara M. Bowen ◽  
Martin Wiedmann ◽  
Kathryn J. Boor
Keyword(s):  
Listeria Monocytogenes ◽  
Sigma Factor ◽  
Deletion Mutation ◽  
Alternative Sigma Factor ◽  
Regulatory Factor ◽  
Virulence Phenotype ◽  
Sigma B

ABSTRACT Transcription of the Listeria monocytogenes positive regulatory factor A protein (PrfA) is initiated from either of two promoters immediately upstream of prfA (prfAp 1 and prfAp 2) or from the upstream plcA promoter. We demonstrate that prfAp 2 is a functional σB-dependent promoter and that a sigB deletion mutation affects the virulence phenotype of L. monocytogenes. Thus, the alternative sigma factor σB contributes to virulence in L. monocytogenes.

scholarly journals Home Alone: Elimination of All but One Alternative Sigma Factor in Listeria monocytogenes Allows Prediction of New Roles for σB

2017 ◽  
Vol 8 ◽  
Author(s):  
Yichang Liu ◽  
Renato H. Orsi ◽  
Kathryn J. Boor ◽  
Martin Wiedmann ◽  
Veronica Guariglia-Oropeza
Keyword(s):  
Listeria Monocytogenes ◽  
Sigma Factor ◽  
Alternative Sigma Factor

scholarly journals Listeria monocytogenes σHContributes to Expression of Competence Genes and Intracellular Growth

2016 ◽  
Vol 198 (8) ◽  
pp. 1207-1217 ◽  
Author(s):  
Veronica Medrano Romero ◽  
Kazuya Morikawa
Keyword(s):  
Transcription Factor ◽  
Listeria Monocytogenes ◽  
Sigma Factor ◽  
Physiological Role ◽  
Population Level ◽  
Alternative Sigma Factor ◽  
Intracellular Growth ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Regulation Scheme

ABSTRACTThe alternative sigma factor σHhas two functions in Gram-positive bacteria: it regulates sporulation and the development of genetic competence.Listeria monocytogenesis a nonsporulating species in which competence has not yet been detected. Nevertheless, the main competence regulators and a series of orthologous genes that form the competence machinery are present in its genome; some of the competence genes play a role in optimal phagosomal escape. In this study, strains overexpressing σHand strains with a σHdeletion were used to elucidate the contribution of σHto the expression of the competence machinery genes inL. monocytogenes. Gene expression analysis showed that σHis, indeed, involved incomGandcomEregulation. Unexpectedly, we observed a unique regulation scheme in which σHand the transcription factor ComK were involved. Population-level analysis showed that even with the overexpression of both factors, only a fraction of the cells expressed the competence machinery genes. Although we could not detect competence, σHwas crucial for phagosomal escape, which implies that this alternative sigma factor has specifically evolved to regulate theL. monocytogenesintracellular life cycle.IMPORTANCEListeria monocytogenescan be an intracellular pathogen capable of causing serious infections in humans and animal species. Recently, the competence machinery genes were described as being necessary for optimal phagosomal escape, in which the transcription factor ComK plays an important role. On the other hand, our previous phylogenetic analysis suggested that the alternative sigma factor σHmight play a role in the regulation of competence genes. The present study shows that some of the competence genes belong to the σHregulon and, importantly, that σHis essential for intracellular growth, implying a unique physiological role of σHamongFirmicutes.

scholarly journals Redefining the Clostridioides difficile σB regulon: σB activates genes involved in detoxifying radicals that can result from the exposure to antimicrobials and hydrogen peroxide

2020 ◽  
Author(s):  
Ilse M. Boekhoud ◽  
Annika-Marisa Michel ◽  
Jeroen Corver ◽  
Dieter Jahn ◽  
Wiep Klaas Smits
Keyword(s):  
Hydrogen Peroxide ◽  
Stress Response ◽  
Sigma Factor ◽  
Gene Activation ◽  
Luciferase Reporter ◽  
Transcriptional Level ◽  
Alternative Sigma Factor ◽  
Gram Positive ◽  
Gram Positive Bacteria ◽  
Sigma B

AbstractIn many gram-positive bacteria the general stress response is regulated at the transcriptional level by the alternative sigma factor sigma B (σB). In C. difficile σB has been implicated in protection against stressors such as reactive oxygen species and antimicrobial compounds. Here, we used an anti-σB antibody to demonstrate time-limited overproduction of σB in C. difficile despite its toxicity at higher cellular concentrations. This toxicity eventually led to the loss of the plasmid used for anhydrotetracycline-induced σB gene expression. Inducible σB overproduction uncouples σB expression from its native regulatory network and allowed for the refinement of the previously proposed σB regulon. At least 32% the regulon was found to consist of genes involved in the response to reactive radicals. Direct gene activation by C. difficile σB was demonstrated through in vitro run-off transcription of specific target genes (cd0350, cd3614, cd3605, cd2963). Finally, we demonstrated that different antimicrobials and hydrogen peroxide induce these genes in a manner dependent on this sigma factor, using a plate-based luciferase reporter assay. Together, our work suggests that lethal exposure to antimicrobials may result in the formation of toxic radicals that lead to σB-dependent gene activation.ImportanceSigma B is the alternative sigma factor governing stress response in many gram-positive bacteria. In C. difficile, a sigB mutant shows pleiotropic transcriptional effects. Here, we determine genes that are likely direct targets of σB by evaluating the transcriptional effects of σB overproduction, provide biochemical evidence of direct transcriptional activation by σB, and show that σB-dependent genes can be activated by antimicrobials. Together our data suggest that σB is a key player in dealing with toxic radicals.

scholarly journals Redefining the Clostridioides difficile σB Regulon: σB Activates Genes Involved in Detoxifying Radicals That Can Result from the Exposure to Antimicrobials and Hydrogen Peroxide

mSphere ◽  
2020 ◽  
Vol 5 (5) ◽  
Author(s):  
Ilse M. Boekhoud ◽  
Annika-Marisa Michel ◽  
Jeroen Corver ◽  
Dieter Jahn ◽  
Wiep Klaas Smits
Keyword(s):  
Hydrogen Peroxide ◽  
Stress Response ◽  
Sigma Factor ◽  
Gene Activation ◽  
Luciferase Reporter ◽  
Alternative Sigma Factor ◽  
Gram Positive ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Sigma B

ABSTRACT In many Gram-positive bacteria, the general stress response is regulated at the transcriptional level by the alternative sigma factor sigma B (σB). In C. difficile, σB has been implicated in protection against stressors such as reactive oxygen species (ROS) and antimicrobial compounds. Here, we used an anti-σB antibody to demonstrate time-limited overproduction of σB in C. difficile despite its toxicity at higher cellular concentrations. This toxicity eventually led to the loss of the plasmid used for anhydrotetracycline-induced σB gene expression. Inducible σB overproduction uncouples σB expression from its native regulatory network and allows for the refinement of the previously proposed σB regulon. At least 32% of the regulon was found to consist of genes involved in the response to reactive radicals. Direct gene activation by C. difficile σB was demonstrated through in vitro runoff transcription of specific target genes (cd0350, cd3614, cd3605, and cd2963). Finally, we demonstrated that different antimicrobials and hydrogen peroxide induce these genes in a manner dependent on this sigma factor, using a plate-based luciferase reporter assay. Together, our work suggests that lethal exposure to antimicrobials may result in the formation of toxic radicals that lead to σB-dependent gene activation. IMPORTANCE Sigma B is the alternative sigma factor governing stress response in many Gram-positive bacteria. In C. difficile, a sigB mutant shows pleiotropic transcriptional effects. Here, we determine genes that are likely direct targets of σB by evaluating the transcriptional effects of σB overproduction, provide biochemical evidence of direct transcriptional activation by σB, and show that σB-dependent genes can be activated by antimicrobials. Together, our data suggest that σB is a key player in dealing with toxic radicals.

scholarly journals The Alternative Sigma Factor σB and the Virulence Gene Regulator PrfA Both Regulate Transcription of Listeria monocytogenes Internalins

2007 ◽  
Vol 73 (9) ◽  
pp. 2919-2930 ◽  
Author(s):  
Patrick McGann ◽  
Martin Wiedmann ◽  
Kathryn J. Boor
Keyword(s):  
Listeria Monocytogenes ◽  
Sigma Factor ◽  
Virulence Genes ◽  
Virulence Gene ◽  
Alternative Sigma Factor ◽  
Transcript Levels ◽  
Virulence Gene Expression ◽  
Reverse Transcription Pcr ◽  
Culture Cells ◽  
Tissue Culture Cells

ABSTRACT Some Listeria monocytogenes internalins are recognized as contributing to invasion of mammalian tissue culture cells. While PrfA is well established as a positive regulator of L. monocytogenes virulence gene expression, the stress-responsive σB has been recognized only recently as contributing to expression of virulence genes, including some that encode internalins. To measure the relative contributions of PrfA and σB to internalin gene transcription, we used reverse transcription-PCR to quantify transcript levels for eight internalin genes (inlA, inlB, inlC, inlC2, inlD, inlE, inlF, and inlG) in L. monocytogenes 10403S and in isogenic ΔprfA, ΔsigB, and ΔsigB ΔprfA strains. Strains were grown under defined conditions to produce (i) active PrfA, (ii) active σB and active PrfA, (iii) inactive PrfA, and (iv) active σB and inactive PrfA. Under the conditions tested, σB and PrfA contributed differentially to the expression of the various internalins such that (i) both σB and PrfA contributed to inlA and inlB transcription, (ii) only PrfA contributed to inlC transcription, (iii) only σB contributed to inlC2 and inlD transcription, and (iv) neither σB nor PrfA contributed to inlF and inlG transcription. inlE transcript levels were undetectable. The important role for σB in regulating expression of L. monocytogenes internalins suggests that exposure of this organism to environmental stress conditions, such as those encountered in the gastrointestinal tract, may activate internalin transcription. Interplay between σB and PrfA also appears to be critical for regulating transcription of some virulence genes, including inlA, inlB, and prfA.

The alternative sigma factor sigma B of Staphylococcus aureus modulates virulence in experimental central venous catheter-related infections

2008 ◽  
Vol 10 (3) ◽  
pp. 217-223 ◽  
Author(s):  
Udo Lorenz ◽  
Christian Hüttinger ◽  
Tina Schäfer ◽  
Wilma Ziebuhr ◽  
Arnulf Thiede ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Central Venous Catheter ◽  
Sigma Factor ◽  
Venous Catheter ◽  
Alternative Sigma Factor ◽  
Central Venous ◽  
Sigma B

scholarly journals The Listeria monocytogenes σB Regulon and Its Virulence-Associated Functions Are Inhibited by a Small Molecule

mBio ◽  
2011 ◽  
Vol 2 (6) ◽  
Author(s):  
M. Elizabeth Palmer ◽  
Soraya Chaturongakul ◽  
Martin Wiedmann ◽  
Kathryn J. Boor
Keyword(s):  
Bacillus Subtilis ◽  
Listeria Monocytogenes ◽  
Small Molecule ◽  
Sigma Factor ◽  
Pathogen Transmission ◽  
Bile Salt Hydrolase ◽  
Alternative Sigma Factor ◽  
Bacterial Survival ◽  
Gram Positive ◽  
Content Type

ABSTRACTThe stress-responsive alternative sigma factor σBis conserved across diverse Gram-positive bacterial genera. InListeria monocytogenes, σBregulates transcription of >150 genes, including genes contributing to virulence and to bacterial survival under host-associated stress conditions, such as those encountered in the human gastrointestinal lumen. An inhibitor ofL. monocytogenesσBactivity was identified by screening ~57,000 natural and synthesized small molecules using a high-throughput cell-based assay. The compound fluoro-phenyl-styrene-sulfonamide (FPSS) (IC50= 3.5 µM) downregulated the majority of genes previously identified as members of the σBregulon inL. monocytogenes10403S, thus generating a transcriptional profile comparable to that of a 10403S ΔsigBstrain. Specifically, of the 208 genes downregulated by FPSS, 75% had been identified previously as positively regulated by σB. Downregulated genes included key virulence and stress response genes, such asinlA,inlB,bsh,hfq,opuC, andbilE. From a functional perspective, FPSS also inhibitedL. monocytogenesinvasion of human intestinal epithelial cells and bile salt hydrolase activity. The ability of FPSS to inhibit σBactivity in bothL. monocytogenesandBacillus subtilisindicates its utility as a specific inhibitor of σBacross multiple Gram-positive genera.IMPORTANCEThe σBtranscription factor regulates expression of genes responsible for bacterial survival under changing environmental conditions and for virulence; therefore, this alternative sigma factor is important for transmission ofL. monocytogenesand other Gram-positive bacteria. Regulation of σBactivity is complex and tightly controlled, reflecting the key role of this factor in bacterial metabolism. We present multiple lines of evidence indicating that fluoro-phenyl-styrene-sulfonamide (FPSS) specifically inhibits activity of σBacross Gram-positive bacterial genera, i.e., in bothListeria monocytogenesandBacillus subtilis. Therefore, FPSS is an important new tool that will enable novel approaches for exploring complex regulatory networks inL. monocytogenesand other Gram-positive pathogens and for investigating small-molecule applications for controlling pathogen transmission.

scholarly journals Identification of a σB-Dependent Small Noncoding RNA in Listeria monocytogenes

2008 ◽  
Vol 190 (18) ◽  
pp. 6264-6270 ◽  
Author(s):  
Jesper Sejrup Nielsen ◽  
Anders Steno Olsen ◽  
Mette Bonde ◽  
Poul Valentin-Hansen ◽  
Birgitte H. Kallipolitis
Keyword(s):  
Listeria Monocytogenes ◽  
Stress Tolerance ◽  
Sigma Factor ◽  
Noncoding Rna ◽  
Noncoding Rnas ◽  
Alternative Sigma Factor ◽  
Dependent Manner ◽  
Small Noncoding Rna ◽  
Small Noncoding Rnas ◽  
Regulatory Circuits

ABSTRACT In Listeria monocytogenes, the alternative sigma factor σB plays important roles in stress tolerance and virulence. Here, we present the identification of SbrA, a novel small noncoding RNA that is produced in a σB-dependent manner. This finding adds the σB regulon to the growing list of stress-induced regulatory circuits that include small noncoding RNAs.

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