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

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 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 Alternative Sigma Factor SigK Has a Role in Stress Tolerance of Group I Clostridium botulinum Strain ATCC 3502

2013 ◽  
Vol 79 (12) ◽  
pp. 3867-3869 ◽  
Author(s):  
Elias Dahlsten ◽  
David Kirk ◽  
Miia Lindström ◽  
Hannu Korkeala
Keyword(s):  
Stress Tolerance ◽  
Sigma Factor ◽  
Clostridium Botulinum ◽  
Alternative Sigma Factor ◽  
Strain Atcc ◽  
Content Type ◽  
Osmotic Stress Tolerance ◽  
Group I ◽  
Temperature Downshift

ABSTRACTThe role of the alternative sigma factor SigK in cold and osmotic stress tolerance ofClostridium botulinumATCC 3502 was demonstrated by induction ofsigKafter temperature downshift and exposure to hyperosmotic conditions and by impaired growth of thesigKmutants under the respective conditions.

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 Mutations of the Listeria monocytogenes PeptidoglycanN-Deacetylase andO-Acetylase Result in Enhanced Lysozyme Sensitivity, Bacteriolysis, and Hyperinduction of Innate Immune Pathways

2011 ◽  
Vol 79 (9) ◽  
pp. 3596-3606 ◽  
Author(s):  
Chris S. Rae ◽  
Aimee Geissler ◽  
Paul C. Adamson ◽  
Daniel A. Portnoy
Keyword(s):  
Listeria Monocytogenes ◽  
Transcriptional Responses ◽  
Gram Positive ◽  
Content Type ◽  
Growth Defects ◽  
Gram Positive Bacteria ◽  
Host Cell Death

ABSTRACTListeria monocytogenesis a Gram-positive intracellular pathogen that is naturally resistant to lysozyme. Recently, it was shown that peptidoglycan modification by N-deacetylation or O-acetylation confers resistance to lysozyme in various Gram-positive bacteria, includingL. monocytogenes.L. monocytogenespeptidoglycan is deacetylated by the action ofN-acetylglucosamine deacetylase (Pgd) and acetylated byO-acetylmuramic acid transferase (Oat). We characterized Pgd−, Oat−, and double mutants to determine the specific role ofL. monocytogenespeptidoglycan acetylation in conferring lysozyme sensitivity during infection of macrophages and mice. Pgd−and Pgd−Oat−double mutants were attenuated approximately 2 and 3.5 logs, respectively,in vivo. In bone-marrow derived macrophages, the mutants demonstrated intracellular growth defects and increased induction of cytokine transcriptional responses that emanated from a phagosome and the cytosol. Lysozyme-sensitive mutants underwent bacteriolysis in the macrophage cytosol, resulting in AIM2-dependent pyroptosis. Each of thein vitrophenotypes was rescued upon infection of LysM−macrophages. The addition of extracellular lysozyme to LysM−macrophages restored cytokine induction, host cell death, andL. monocytogenesgrowth inhibition. This surprising observation suggests that extracellular lysozyme can access the macrophage cytosol and act on intracellular lysozyme-sensitive bacteria.

scholarly journals Role for GrgA in Regulation of σ28-Dependent Transcription in the Obligate Intracellular Bacterial PathogenChlamydia trachomatis

2018 ◽  
Vol 200 (20) ◽  
Author(s):  
Malhar Desai ◽  
Wurihan Wurihan ◽  
Rong Di ◽  
Joseph D. Fondell ◽  
Bryce E. Nickels ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Chlamydia Trachomatis ◽  
Sigma Factor ◽  
Bacterial Pathogen ◽  
Direct Interaction ◽  
Developmental Cycle ◽  
Content Type ◽  
Sexually Transmitted ◽  
Obligate Intracellular ◽  
Specific Transcription Factor

ABSTRACTThe obligate intracellular bacterial pathogenChlamydia trachomatishas a unique developmental cycle consisting of two contrasting cellular forms. Whereas the primaryChlamydiasigma factor, σ66, is involved in the expression of the majority of chlamydial genes throughout the developmental cycle, expression of several late genes requires the alternative sigma factor, σ28. In prior work, we identified GrgA as aChlamydia-specific transcription factor that activates σ66-dependent transcription by binding DNA and interacting with a nonconserved region (NCR) of σ66. Here, we extend these findings by showing GrgA can also activate σ28-dependent transcription through direct interaction with σ28. We measure the binding affinity of GrgA for both σ66and σ28, and we identify regions of GrgA important for σ28-dependent transcription. Similar to results obtained with σ66, we find that GrgA's interaction with σ28involves an NCR located upstream of conserved region 2 of σ28. Our findings suggest that GrgA is an important regulator of both σ66- and σ28-dependent transcription inC. trachomatisand further highlight NCRs of bacterial RNA polymerase as targets for regulatory factors unique to particular organisms.IMPORTANCEChlamydia trachomatisis the number one sexually transmitted bacterial pathogen worldwide. A substantial proportion ofC. trachomatis-infected women develop infertility, pelvic inflammatory syndrome, and other serious complications.C. trachomatisis also a leading infectious cause of blindness in underdeveloped countries. The pathogen has a unique developmental cycle that is transcriptionally regulated. The discovery of an expanded role for theChlamydia-specific transcription factor GrgA helps us understand the progression of the chlamydial developmental cycle.

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 Resilience in the Face of Uncertainty: Sigma Factor B Fine-Tunes Gene Expression To Support Homeostasis in Gram-Positive Bacteria

2016 ◽  
Vol 82 (15) ◽  
pp. 4456-4469 ◽  
Author(s):  
Claudia Guldimann ◽  
Kathryn J. Boor ◽  
Martin Wiedmann ◽  
Veronica Guariglia-Oropeza
Keyword(s):  
Gene Expression ◽  
Sigma Factor ◽  
Environmental Changes ◽  
Regulation Of Gene Expression ◽  
Bacterial Survival ◽  
Gram Positive ◽  
Content Type ◽  
Gram Positive Bacteria ◽  
Changing Environments ◽  
The Face

ABSTRACTGram-positive bacteria are ubiquitous and diverse microorganisms that can survive and sometimes even thrive in continuously changing environments. The key to such resilience is the ability of members of a population to respond and adjust to dynamic conditions in the environment. In bacteria, such responses and adjustments are mediated, at least in part, through appropriate changes in the bacterial transcriptome in response to the conditions encountered. Resilience is important for bacterial survival in diverse, complex, and rapidly changing environments and requires coordinated networks that integrate individual, mechanistic responses to environmental cues to enable overall metabolic homeostasis. In many Gram-positive bacteria, a key transcriptional regulator of the response to changing environmental conditions is the alternative sigma factor σB. σBhas been characterized in a subset of Gram-positive bacteria, including the generaBacillus,Listeria, andStaphylococcus. Recent insight from next-generation-sequencing results indicates that σB-dependent regulation of gene expression contributes to resilience, i.e., the coordination of complex networks responsive to environmental changes. This review explores contributions of σBto resilience inBacillus,Listeria, andStaphylococcusand illustrates recently described regulatory functions of σB.

scholarly journals Two Zinc Uptake Systems Contribute to the Full Virulence of Listeria monocytogenes during GrowthIn VitroandIn Vivo

2011 ◽  
Vol 80 (1) ◽  
pp. 14-21 ◽  
Author(s):  
David Corbett ◽  
Jiahui Wang ◽  
Stephanie Schuler ◽  
Gloria Lopez-Castejon ◽  
Sarah Glenn ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Zinc Uptake ◽  
Detectable Effect ◽  
Intracellular Growth ◽  
Content Type ◽  
Zinc Sensing ◽  
Identification And Characterization ◽  
Cell Deletion

ABSTRACTWe report here the identification and characterization of two zinc uptake systems, ZurAM and ZinABC, in the intracellular pathogenListeria monocytogenes. Transcription of both operons was zinc responsive and regulated by the zinc-sensing repressor Zur. Deletion of eitherzurAMorzinAhad no detectable effect on growth in defined media, but a doublezurAM zinAmutant was unable to grow in the absence of zinc supplementation. Deletion ofzinAhad no detectable effect on intracellular growth in HeLa epithelial cells. In contrast, growth of thezurAMmutant was significantly impaired in these cells, indicating the importance of the ZurAM system during intracellular growth. Notably, the deletion of bothzinAandzurAMseverely attenuated intracellular growth, with the double mutant being defective in actin-based motility and unable to spread from cell to cell. Deletion of eitherzurAMorzinAhad a significant effect on virulence in an oral mouse model, indicating that both zinc uptake systems are importantin vivoand establishing the importance of zinc acquisition during infection byL. monocytogenes. The presence of two zinc uptake systems may offer a mechanism by whichL. monocytogenescan respond to zinc deficiency within a variety of environments and during different stages of infection, with each system making distinct contributions under different stress conditions.

scholarly journals prfA-Like Transcription Factor Genelmo0753Contributes to l-Rhamnose Utilization in Listeria monocytogenes Strains Associated with Human Food-Borne Infections

2013 ◽  
Vol 79 (18) ◽  
pp. 5584-5592 ◽  
Author(s):  
Joelle K. Salazar ◽  
Zhuchun Wu ◽  
P. David McMullen ◽  
Qin Luo ◽  
Nancy E. Freitag ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Listeria Monocytogenes ◽  
Bacterial Pathogen ◽  
Phenol Red ◽  
Flagellar Motility ◽  
Content Type ◽  
Genetic Lineages ◽  
Functional Roles ◽  
Food Borne ◽  
Virulence Regulator

ABSTRACTListeria monocytogenesis a food-borne bacterial pathogen and the causative agent of human and animal listeriosis. Among the three major genetic lineages ofL. monocytogenes(i.e., LI, LII, and LIII), LI and LII are predominantly associated with food-borne listeriosis outbreaks, whereas LIII is rarely implicated in human infections. In a previous study, we identified a Crp/Fnr family transcription factor gene,lmo0753, that was highly specific to outbreak-associated LI and LII but absent from LIII. Lmo0753 shares two conserved functional domains, including a DNA binding domain, with the well-characterized master virulence regulator PrfA inL. monocytogenes. In this study, we constructedlmo0753deletion and complementation mutants in two fully sequencedL. monocytogenesLII strains, 10403S and EGDe, and compared the flagellar motility, phospholipase C production, hemolysis, and intracellular growth of the mutants and their respective wild types. Our results suggested thatlmo0753plays a role in hemolytic activity in both EGDe and 10403S. More interestingly, we found that deletion oflmo0753led to the loss ofl-rhamnose utilization in EGDe, but not in 10403S. RNA-seq analysis of EGDe Δ0753incubated in phenol red medium containingl-rhamnose as the sole carbon source revealed that 126 (4.5%) and 546 (19.5%) out of 2,798 genes in the EGDe genome were up- and downregulated more than 2-fold, respectively, compared to the wild-type strain. Genes related to biotin biosynthesis, general stress response, and rhamnose metabolism were shown to be differentially regulated. Findings from this study collectively suggested varied functional roles oflmo0753in different LIIL. monocytogenesstrain backgrounds associated with human listeriosis outbreaks.

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