scholarly journals Vibrio cholerae OmpR Represses the ToxR Regulon in Response to Membrane Intercalating Agents That Are Prevalent in the Human Gastrointestinal Tract

2019 ◽  
Vol 88 (3) ◽  
Author(s):  
D. E. Kunkle ◽  
T. F. Bina ◽  
X. R. Bina ◽  
J. E. Bina
Keyword(s):  
Gastrointestinal Tract ◽  
Vibrio Cholerae ◽  
Virulence Factor ◽  
Diarrheal Disease ◽  
Multidrug Efflux ◽  
Content Type ◽  
Factor Production ◽  
Resistance Nodulation Division ◽  
Intercalating Agents ◽  
Virulence Factor Production

ABSTRACT Multidrug efflux systems belonging to the resistance-nodulation-division (RND) superfamily are ubiquitous in Gram-negative bacteria. RND efflux systems are often associated with multiple antimicrobial resistance and also contribute to the expression of diverse bacterial phenotypes including virulence, as documented in the intestinal pathogen Vibrio cholerae, the causative agent of the severe diarrheal disease cholera. Transcriptomic studies with RND efflux-negative V. cholerae suggested that RND-mediated efflux was required for homeostasis, as loss of RND efflux resulted in the activation of transcriptional regulators, including multiple environmental sensing systems. In this report, we investigated six RND efflux-responsive regulatory genes for contributions to V. cholerae virulence factor production. Our data showed that the V. cholerae gene VC2714, encoding a homolog of Escherichia coli OmpR, was a virulence repressor. The expression of ompR was elevated in an RND-null mutant, and ompR deletion partially restored virulence factor production in the RND-negative background. Virulence inhibitory activity in the RND-negative background resulted from OmpR repression of the key ToxR regulon virulence activator aphB, and ompR overexpression in wild-type cells also repressed virulence through aphB. We further show that ompR expression was not altered by changes in osmolarity but instead was induced by membrane-intercalating agents that are prevalent in the host gastrointestinal tract and which are substrates of the V. cholerae RND efflux systems. Our collective results indicate that V. cholerae ompR is an aphB repressor and regulates the expression of the ToxR virulence regulon in response to novel environmental cues.

scholarly journals Vibrio cholerae OmpR represses the ToxR regulon in response to membrane intercalating agents that are prevalent in the human gastrointestinal tract

2019 ◽  
Author(s):  
DE Kunkle ◽  
TF Bina ◽  
XR Bina ◽  
JE Bina
Keyword(s):  
Gastrointestinal Tract ◽  
Vibrio Cholerae ◽  
Virulence Factor ◽  
Diarrheal Disease ◽  
Multidrug Efflux ◽  
Factor Production ◽  
Resistance Nodulation Division ◽  
Intestinal Pathogen ◽  
Intercalating Agents ◽  
Virulence Factor Production

ABSTRACTMultidrug efflux systems belonging Resistance-Nodulation-Division (RND) superfamily are ubiquitous in Gram-negative bacteria. RND efflux systems are often associated with multiple antimicrobial resistance but also contribute to the expression of diverse bacterial phenotypes including virulence, as documented in the intestinal pathogen Vibrio cholerae, the causative agent of the severe diarrheal disease cholera. Transcriptomic studies with RND efflux-negative V. cholerae suggested that RND-mediated efflux was required for homeostasis, as loss of RND efflux resulted in the activation of transcriptional regulators, including multiple environmental sensing systems. In this report we investigated six RND efflux responsive regulatory genes for contributions to V. cholerae virulence factor production. Our data showed that V. cholerae gene VC2714, encoding a homologue of Escherichia coli OmpR, was a virulence repressor. The expression of ompR was elevated in an RND-null mutant and ompR deletion partially restored virulence factor production in the RND-negative background. Virulence inhibitory activity in the RND-negative background resulted from OmpR repression of the key ToxR regulon virulence activator aphB, and ompR overexpression in WT cells also repressed virulence through aphB. We further show that ompR expression was not altered by changes in osmolarity, but instead was induced by membrane intercalating agents that are prevalent in the host gastrointestinal tract, and which are substrates of the V. cholerae RND efflux systems. Our collective results indicate that V. cholerae ompR is an aphB repressor and regulates the expression of the ToxR virulence regulon in response to novel environmental cues.

scholarly journals Vibrio cholerae ToxR Downregulates Virulence Factor Production in Response to Cyclo(Phe-Pro)

mBio ◽  
2013 ◽  
Vol 4 (5) ◽  
Author(s):  
X. Renee Bina ◽  
Dawn L. Taylor ◽  
Amit Vikram ◽  
Vanessa M. Ante ◽  
James E. Bina
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Virulence Factor ◽  
Virulence Gene ◽  
Enteric Bacteria ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Factor Production ◽  
Virulence Regulator ◽  
Virulence Factor Production

ABSTRACTVibrio choleraeis an aquatic organism that causes the severe acute diarrheal disease cholera. The ability ofV. choleraeto cause disease is dependent upon the production of two critical virulence determinants, cholera toxin (CT) and the toxin-coregulated pilus (TCP). The expression of the genes that encode for CT and TCP production is under the control of a hierarchical regulatory system called the ToxR regulon, which functions to activate virulence gene expression in response toin vivostimuli. Cyclic dipeptides have been found to be produced by numerous bacteria, yet their biological function remains unknown.V. choleraehas been shown to produce cyclo(Phe-Pro). Previous studies in our laboratory demonstrated that cyclo(Phe-Pro) inhibitedV. choleraevirulence factor production. For this study, we report on the mechanism by which cyclo(Phe-Pro) inhibited virulence factor production. We have demonstrated that exogenous cyclo(Phe-Pro) activated the expression ofleuO, a LysR-family regulator that had not been previously associated withV. choleraevirulence. IncreasedleuOexpression repressedaphAtranscription, which resulted in downregulation of the ToxR regulon and attenuated CT and TCP production. The cyclo(Phe-Pro)-dependent induction ofleuOexpression was found to be dependent upon the virulence regulator ToxR. Cyclo(Phe-Pro) did not affecttoxRtranscription or ToxR protein levels but appeared to enhance the ToxR-dependent transcription ofleuO. These results have identifiedleuOas a new component of the ToxR regulon and demonstrate for the first time that ToxR is capable of downregulating virulence gene expression in response to an environmental cue.IMPORTANCEThe ToxR regulon has been a focus of cholera research for more than three decades. During this time, a model has emerged wherein ToxR functions to activate the expression ofVibrio choleraevirulence factors upon host entry.V. choleraeand other enteric bacteria produce cyclo(Phe-Pro), a cyclic dipeptide that we identified as an inhibitor ofV. choleraevirulence factor production. This finding suggested that cyclo(Phe-Pro) was a negative effector of virulence factor production and represented a molecule that could potentially be exploited for therapeutic development. In this work, we investigated the mechanism by which cyclo(Phe-Pro) inhibited virulence factor production. We found that cyclo(Phe-Pro) signaled through ToxR to activate the expression ofleuO, a new virulence regulator that functioned to repress virulence factor production. Our results have identified a new arm of the ToxR regulon and suggest that ToxR may play a broader role in pathogenesis than previously known.

scholarly journals Cyclo(valine–valine) inhibits Vibrio cholerae virulence gene expression

Microbiology ◽  
2014 ◽  
Vol 160 (6) ◽  
pp. 1054-1062 ◽  
Author(s):  
Amit Vikram ◽  
Vanessa M. Ante ◽  
X. Renee Bina ◽  
Qin Zhu ◽  
Xinyu Liu ◽  
...  
Keyword(s):  
Vibrio Cholerae ◽  
Virulence Factor ◽  
Inhibitory Activity ◽  
Virulence Gene ◽  
Side Chains ◽  
Cyclic Dipeptides ◽  
Virulence Gene Expression ◽  
Factor Production ◽  
Virulence Regulator ◽  
Virulence Factor Production

Vibrio cholerae has been shown to produce a cyclic dipeptide, cyclo(phenylalanine–proline) (cFP), that functions to repress virulence factor production. The objective of this study was to determine if heterologous cyclic dipeptides could repress V. cholerae virulence factor production. To that end, three synthetic cyclic dipeptides that differed in their side chains from cFP were assayed for virulence inhibitory activity in V. cholerae. The results revealed that cyclo(valine–valine) (cVV) inhibited virulence factor production by a ToxR-dependent process that resulted in the repression of the virulence regulator aphA. cVV-dependent repression of aphA was found to be independent of known aphA regulatory genes. The results demonstrated that V. cholerae was able to respond to exogenous cyclic dipeptides and implicated the hydrophobic amino acid side chains on both arms of the cyclo dipeptide scaffold as structural requirements for inhibitory activity. The results further suggest that cyclic dipeptides have potential as therapeutics for cholera treatment.

scholarly journals The Vibrio cholerae RND efflux systems impact virulence factor production and adaptive responses via periplasmic sensor proteins

2018 ◽  
Vol 14 (1) ◽  
pp. e1006804 ◽  
Author(s):  
X. Renee Bina ◽  
Mondraya F. Howard ◽  
Dawn L. Taylor-Mulneix ◽  
Vanessa M. Ante ◽  
Dillon E. Kunkle ◽  
...  
Keyword(s):  
Vibrio Cholerae ◽  
Virulence Factor ◽  
Adaptive Responses ◽  
Factor Production ◽  
Sensor Proteins ◽  
Virulence Factor Production

scholarly journals Indole Inhibits ToxR Regulon Expression inVibrio cholerae

2019 ◽  
Vol 87 (3) ◽  
Author(s):  
Mondraya F. Howard ◽  
X. Renee Bina ◽  
James E. Bina
Keyword(s):  
Virulence Factor ◽  
Virulence Gene ◽  
Dependent Manner ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Type Vi Secretion ◽  
Biofilm Production ◽  
Factor Production ◽  
Periplasmic Domain ◽  
Virulence Factor Production

ABSTRACTIndole is a degradation product of tryptophan that functions as a signaling molecule in many bacteria. This includesVibrio cholerae, where indole was shown to regulate biofilm and type VI secretion in nontoxigenic environmental isolates. Indole is also produced by toxigenicV. choleraestrains in the human intestine, but its significance in the host is unknown. We investigated the effects of indole on toxigenicV. choleraeO1 El Tor during growth under virulence inducing conditions. The indole transcriptome was defined by RNA sequencing and showed widespread changes in the expression of genes involved in metabolism, biofilm production, and virulence factor production. In contrast, genes involved in type VI secretion were not affected by indole. We subsequently found that indole repressed genes involved inV. choleraepathogenesis, including the ToxR virulence regulon. Consistent with this, indole inhibited cholera toxin and toxin-coregulated pilus production in a dose-dependent manner. The effects of indole on virulence factor production and biofilm were linked to ToxR and the ToxR-dependent regulator LeuO. The expression ofleuOwas increased by exogenous indole and linked to repression of the ToxR virulence regulon. This process was dependent on the ToxR periplasmic domain, suggesting that indole was a ToxR agonist. This conclusion was further supported by results showing that the ToxR periplasmic domain contributed to indole-mediated increased biofilm production. Collectively, our results suggest that indole may be a niche-specific cue that can function as a ToxR agonist to modulate virulence gene expression and biofilm production inV. cholerae.

scholarly journals Staphylococcus aureus Formyl-Methionyl Transferase Mutants Demonstrate Reduced Virulence Factor Production and Pathogenicity

2013 ◽  
Vol 57 (7) ◽  
pp. 2929-2936 ◽  
Author(s):  
Thomas Lewandowski ◽  
Jianzhong Huang ◽  
Frank Fan ◽  
Shannon Rogers ◽  
Daniel Gentry ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Virulence Factor ◽  
Survival Rates ◽  
Extracellular Proteins ◽  
High Survival ◽  
Invasive Infection ◽  
Loss Of Function ◽  
Content Type ◽  
Factor Production ◽  
Virulence Factor Production

ABSTRACTInhibitors of peptide deformylase (PDF) represent a new class of antibacterial agents with a novel mechanism of action. Mutations that inactivate formyl methionyl transferase (FMT), the enzyme that formylates initiator methionyl-tRNA, lead to an alternative initiation of protein synthesis that does not require deformylation and are the predominant cause of resistance to PDF inhibitors inStaphylococcus aureus. Here, we report that loss-of-function mutations in FMT impart pleiotropic effects that include a reduced growth rate, a nonhemolytic phenotype, and a drastic reduction in production of multiple extracellular proteins, including key virulence factors, such as α-hemolysin and Panton-Valentine leukocidin (PVL), that have been associated withS. aureuspathogenicity. Consequently,S. aureusFMT mutants are greatly attenuated in neutropenic and nonneutropenic murine pyelonephritis infection models and show very high survival rates compared with wild-typeS. aureus. These newly discovered effects on extracellular virulence factor production demonstrate that FMT-null mutants have a more severe fitness cost than previously anticipated, leading to a substantial loss of pathogenicity and a restricted ability to produce an invasive infection.

scholarly journals ToxR mediates the antivirulence activity of phenyl-arginine-β-naphthylamide to attenuate Vibrio cholerae virulence.

2021 ◽  
Author(s):  
Yuding Weng ◽  
Thomas F. Bina ◽  
X. Renee Bina ◽  
James E. Bina
Keyword(s):  
Antimicrobial Resistance ◽  
Vibrio Cholerae ◽  
Virulence Factor ◽  
Efflux Pump ◽  
Feedback Mechanism ◽  
Gram Negative ◽  
Factor Production ◽  
Regulatory Circuit ◽  
Efflux Pump Inhibitors ◽  
Virulence Factor Production

Multidrug efflux systems belonging to the resistance-nodulation-cell division (RND) family are ubiquitous in Gram negative bacteria and critical for antimicrobial resistance. This realization has led to efforts to develop efflux pump inhibitors (EPI) for use as adjuvants for antibiotic treatment of resistant organisms. However, the functions of RND transporters extend beyond antimicrobial resistance to include physiological functions that are critical for pathogenesis, suggesting that EPIs could also be used as antivirulence therapeutics. This was documented in the enteric pathogen Vibrio cholerae where EPIs were shown to attenuate the production of the critical virulence factors cholera toxin (CT) and the toxin coregulated pilus (TCP). In this study we investigated the antivirulence mechanism of action of the EPI phenyl-arginine-β-naphthylamide (PAβN) on V. cholerae. Using bioassays, we documented that PAβN inhibited virulence factor production in three epidemic V. cholerae isolates. Transcriptional reporter studies and mutant analysis indicated that PAβN initiated a ToxR-dependent regulatory circuit to activate leuO expression and that LeuO repressed the expression of the critical virulence activator aphA to attenuate CT and TCP production. The antivirulence activity of PAβN was found to be dependent on the ToxR periplasmic sensing domain suggesting that a feedback mechanism was involved in its activity. Collectively the data indicated that PAβN inhibited V. cholerae virulence factor production by activating a ToxR-dependent metabolic feedback mechanism to repress the expression of the ToxR virulence regulon. This suggests that efflux pump inhibitors could be used as antivirulence therapeutics for the treatment of cholera and perhaps other gram negative pathogens.

scholarly journals The 58th Cysteine of TcpP Is Essential for Vibrio cholerae Virulence Factor Production and Pathogenesis

2020 ◽  
Vol 11 ◽  
Author(s):  
Mengting Shi ◽  
Na Li ◽  
Yuanyuan Xue ◽  
Zengtao Zhong ◽  
Menghua Yang
Keyword(s):  
Vibrio Cholerae ◽  
Virulence Factor ◽  
Factor Production ◽  
Virulence Factor Production

scholarly journals Regulation of Vibrio Polysaccharide Synthesis and Virulence Factor Production by CdgC, a GGDEF-EAL Domain Protein, in Vibrio cholerae

2007 ◽  
Vol 189 (3) ◽  
pp. 717-729 ◽  
Author(s):  
Bentley Lim ◽  
Sinem Beyhan ◽  
Fitnat H. Yildiz
Keyword(s):  
Vibrio Cholerae ◽  
Virulence Factor ◽  
Stationary Phases ◽  
Cellular Processes ◽  
Factor Production ◽  
Expression Of Genes ◽  
Flagellar Biosynthesis ◽  
Polysaccharide Synthesis ◽  
Regulator Genes ◽  
Virulence Factor Production

ABSTRACT In Vibrio cholerae, the second messenger 3′,5′-cyclic diguanylic acid (c-di-GMP) regulates several cellular processes, such as formation of corrugated colony morphology, biofilm formation, motility, and virulence factor production. Both synthesis and degradation of c-di-GMP in the cell are modulated by proteins containing GGDEF and/or EAL domains, which function as a diguanylate cyclase and a phosphodiesterase, respectively. The expression of two genes, cdgC and mbaA, which encode proteins harboring both GGDEF and EAL domains is higher in the rugose phase variant of V. cholerae than in the smooth variant. In this study, we carried out gene expression analysis to determine the genes regulated by CdgC in the rugose and smooth phase variants of V. cholerae. We determined that CdgC regulates expression of genes required for V. cholerae polysaccharide synthesis and of the transcriptional regulator genes vpsR, vpsT, and hapR. CdgC also regulates expression of genes involved in extracellular protein secretion, flagellar biosynthesis, and virulence factor production. We then compared the genes regulated by CdgC and by MbaA, during both exponential and stationary phases of growth, to elucidate processes regulated by them. Identification of the regulons of CdgC and MbaA revealed that the regulons overlap, but the timing of regulation exerted by CdgC and MbaA is different, suggesting the interplay and complexity of the c-di-GMP signal transduction pathways operating in V. cholerae.

scholarly journals Staphylococcal Virulence Factors on the Skin of Atopic Dermatitis Patients

mSphere ◽  
2019 ◽  
Vol 4 (6) ◽  
Author(s):  
Mary C. Moran ◽  
Michael P. Cahill ◽  
Matthew G. Brewer ◽  
Takeshi Yoshida ◽  
Sara Knowlden ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Atopic Dermatitis ◽  
Virulence Factors ◽  
Virulence Factor ◽  
Protein Level ◽  
Content Type ◽  
Factor Production ◽  
First Time ◽  
Virulence Factor Production ◽  
Specific Virulence

ABSTRACT Staphylococcus aureus is the leading cause of skin and soft tissue infections, bacteremia, infective endocarditis, osteoarticular, pleuropulmonary, and device-related infections. Virulence factors secreted by S. aureus, including superantigens and cytotoxins, play significant roles in driving disease. The ability to identify virulence factors present at the site of infection will be an important tool in better identifying and understanding how specific virulence factors contribute to disease. Previously, virulence factor production has been determined by culturing S. aureus isolates and detecting the mRNA of specific virulence factors. We demonstrated for the first time that virulence factors can be directly detected at the protein level from human samples, removing the need to first culture isolated bacteria. Superantigens and cytotoxins were detected and quantified with a Western dot blot assay by using reconstituted skin swabs obtained from patients with atopic dermatitis. This methodology will significantly enhance our ability to investigate the complex host-microbe environment and the effects various therapies have on virulence factor production. Overall, the ability to directly quantify virulence factors present at the site of infection or colonization will enhance our understanding of S. aureus-related diseases and help identify optimal treatments. IMPORTANCE For the first time, we show that secreted staphylococcal virulence factors can be quantified at the protein level directly from skin swabs obtained from the skin of atopic dermatitis patients. This technique eliminates the need to culture Staphylococcus aureus and then test the strain’s potential to produce secreted virulence factors. Our methodology shows that secreted virulence factors are present on the skin of atopic patients and provides a more accurate means of evaluating the physiological impact of S. aureus in inflammatory diseases such as atopic dermatitis.

Sign in / Sign up

Export Citation Format

Share Document