scholarly journals Binding site requirements of the virulence gene regulator AphB: differential affinities for the Vibrio cholerae classical and El Tor tcpPH promoters

2002 ◽  
Vol 44 (2) ◽  
pp. 533-547 ◽  
Author(s):  
Gabriela Kovacikova ◽  
Karen Skorupski
Keyword(s):  
Binding Site ◽  
Vibrio Cholerae ◽  
Virulence Gene ◽  
El Tor

scholarly journals The Cpx System Regulates Virulence Gene Expression in Vibrio cholerae

2015 ◽  
Vol 83 (6) ◽  
pp. 2396-2408 ◽  
Author(s):  
Nicole Acosta ◽  
Stefan Pukatzki ◽  
Tracy L. Raivio
Keyword(s):  
Vibrio Cholerae ◽  
Response Regulator ◽  
Bacterial Species ◽  
Virulence Gene ◽  
Receptor Protein ◽  
Virulence Determinants ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Envelope Stress ◽  
El Tor

Bacteria possess signal transduction pathways capable of sensing and responding to a wide variety of signals. The Cpx envelope stress response, composed of the sensor histidine kinase CpxA and the response regulator CpxR, senses and mediates adaptation to insults to the bacterial envelope. The Cpx response has been implicated in the regulation of a number of envelope-localized virulence determinants across bacterial species. Here, we show that activation of the Cpx pathway inVibrio choleraeEl Tor strain C6706 leads to a decrease in expression of the major virulence factors in this organism, cholera toxin (CT) and the toxin-coregulated pilus (TCP). Our results indicate that this occurs through the repression of production of the ToxT regulator and an additional upstream transcription factor, TcpP. The effect of the Cpx response on CT and TCP expression is mostly abrogated in a cyclic AMP receptor protein (CRP) mutant, although expression of thecrpgene is unaltered. Since TcpP production is controlled by CRP, our data suggest a model whereby the Cpx response affects CRP function, which leads to diminished TcpP, ToxT, CT, and TCP production.

scholarly journals Integration of Cyclic di-GMP and Quorum Sensing in the Control ofvpsTandaphAin Vibrio cholerae

2011 ◽  
Vol 193 (22) ◽  
pp. 6331-6341 ◽  
Author(s):  
Disha Srivastava ◽  
Rebecca C. Harris ◽  
Christopher M. Waters
Keyword(s):  
Quorum Sensing ◽  
Binding Site ◽  
Vibrio Cholerae ◽  
Biofilm Formation ◽  
Virulence Gene ◽  
Transcriptional Activator ◽  
Transcriptional Regulators ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Signaling Systems

Vibrio choleraetransitions between aquatic environmental reservoirs and infection in the gastrointestinal tracts of human hosts. The second-messenger molecule cyclic di-GMP (c-di-GMP) and quorum sensing (QS) are important signaling systems that enableV. choleraeto alternate between these distinct environments by controlling biofilm formation and virulence factor expression. Here we identify a conserved regulatory mechanism inV. choleraethat integrates c-di-GMP and QS to control the expression of two transcriptional regulators:aphA, an activator of virulence gene expression and an important regulator of the quorum-sensing pathway, andvpsT, a transcriptional activator that induces biofilm formation. Surprisingly,aphAexpression was induced by c-di-GMP. Activation of bothaphAandvpsTby c-di-GMP requires the transcriptional activator VpsR, which binds to c-di-GMP. The VpsR binding site at each of these promoters overlaps with the binding site of HapR, the master QS regulator at high cell densities. Our results suggest thatV. choleraecombines information conveyed by QS and c-di-GMP to appropriately respond and adapt to divergent environments by modulating the expression of key transcriptional regulators.

scholarly journals A Vibrio cholerae LysR Homolog, AphB, Cooperates with AphA at the tcpPH Promoter To Activate Expression of the ToxR Virulence Cascade

1999 ◽  
Vol 181 (14) ◽  
pp. 4250-4256 ◽  
Author(s):  
Gabriela Kovacikova ◽  
Karen Skorupski
Keyword(s):  
Vibrio Cholerae ◽  
Virulence Genes ◽  
Virulence Gene ◽  
Growth Conditions ◽  
Culture Conditions ◽  
Virulence Gene Expression ◽  
Environmental Stimuli ◽  
High Level ◽  
El Tor

ABSTRACT We describe here a new member of the LysR family of transcriptional regulators, AphB, which is required for activation of the Vibrio cholerae ToxR virulence cascade. AphB activates the transcription of the tcpPH operon in response to environmental stimuli, and this process requires cooperation with a second protein, AphA. The expression of neither aphA or aphB is strongly regulated by environmental stimuli, raising the possibility that the activities of the proteins themselves may be influenced under various conditions. Strains of the El Tor biotype of V. choleraetypically exhibit lower expression of ToxR-regulated virulence genes in vitro than classical strains and require specialized culture conditions (AKI medium) to induce high-level expression. We show here that expression of aphB from the tac promoter in El Tor biotype strains dramatically increases virulence gene expression to levels similar to those observed in classical strains under all growth conditions examined. These results suggest that AphB plays a role in the differential regulation of virulence genes between the two disease-causing biotypes.

scholarly journals Bicarbonate Induces Vibrio cholerae Virulence Gene Expression by Enhancing ToxT Activity

2009 ◽  
Vol 77 (9) ◽  
pp. 4111-4120 ◽  
Author(s):  
Basel H. Abuaita ◽  
Jeffrey H. Withey
Keyword(s):  
Gene Expression ◽  
Carbonic Anhydrase ◽  
Vibrio Cholerae ◽  
Regulatory Protein ◽  
Virulence Gene ◽  
Chemical Stimulus ◽  
High Concentration ◽  
Virulence Gene Expression ◽  
Regulatory Cascade ◽  
El Tor

ABSTRACT Vibrio cholerae is a gram-negative bacterium that is the causative agent of cholera, a severe diarrheal illness. The two biotypes of V. cholerae O1 capable of causing cholera, classical and El Tor, require different in vitro growth conditions for induction of virulence gene expression. Growth under the inducing conditions or infection of a host initiates a complex regulatory cascade that results in production of ToxT, a regulatory protein that directly activates transcription of the genes encoding cholera toxin (CT), toxin-coregulated pilus (TCP), and other virulence genes. Previous studies have shown that sodium bicarbonate induces CT expression in the V. cholerae El Tor biotype. However, the mechanism for bicarbonate-mediated CT induction has not been defined. In this study, we demonstrate that bicarbonate stimulates virulence gene expression by enhancing ToxT activity. Both the classical and El Tor biotypes produce inactive ToxT protein when they are cultured statically in the absence of bicarbonate. Addition of bicarbonate to the culture medium does not affect ToxT production but causes a significant increase in CT and TCP expression in both biotypes. Ethoxyzolamide, a potent carbonic anhydrase inhibitor, inhibits bicarbonate-mediated virulence induction, suggesting that conversion of CO2 into bicarbonate by carbonic anhydrase plays a role in virulence induction. Thus, bicarbonate is the first positive effector for ToxT activity to be identified. Given that bicarbonate is present at high concentration in the upper small intestine where V. cholerae colonizes, bicarbonate is likely an important chemical stimulus that V. cholerae senses and that induces virulence during the natural course of infection.

scholarly journals The Fatty Acid Regulator FadR Influences the Expression of the Virulence Cascade in the El Tor Biotype of Vibrio cholerae by Modulating the Levels of ToxT via Two Different Mechanisms

2017 ◽  
Vol 199 (7) ◽  
Author(s):  
Gabriela Kovacikova ◽  
Wei Lin ◽  
Ronald K. Taylor ◽  
Karen Skorupski
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Virulence Gene ◽  
Enteric Bacteria ◽  
Posttranslational Regulation ◽  
Content Type ◽  
Virulence Gene Expression ◽  
Expression Of Genes ◽  
El Tor ◽  
Virulence Regulator

ABSTRACT FadR is a master regulator of fatty acid (FA) metabolism that coordinates the pathways of FA degradation and biosynthesis in enteric bacteria. We show here that a ΔfadR mutation in the El Tor biotype of Vibrio cholerae prevents the expression of the virulence cascade by influencing both the transcription and the posttranslational regulation of the master virulence regulator ToxT. FadR is a transcriptional regulator that represses the expression of genes involved in FA degradation, activates the expression of genes involved in unsaturated FA (UFA) biosynthesis, and also activates the expression of two operons involved in saturated FA (SFA) biosynthesis. Since FadR does not bind directly to the toxT promoter, we determined whether the regulation of any of its target genes indirectly influenced ToxT. This was accomplished by individually inserting a double point mutation into the FadR-binding site in the promoter of each target gene, thereby preventing their activation or repression. Although preventing FadR-mediated activation of fabA, which encodes the enzyme that carries out the first step in UFA biosynthesis, did not significantly influence either the transcription or the translation of ToxT, it reduced its levels and prevented virulence gene expression. In the mutant strain unable to carry out FadR-mediated activation of fabA, expressing fabA ectopically restored the levels of ToxT and virulence gene expression. Taken together, the results presented here indicate that V. cholerae FadR influences the virulence cascade in the El Tor biotype by modulating the levels of ToxT via two different mechanisms. IMPORTANCE Fatty acids (FAs) play important roles in membrane lipid homeostasis and energy metabolism in all organisms. In Vibrio cholerae, the causative agent of the acute intestinal disease cholera, they also influence virulence by binding into an N-terminal pocket of the master virulence regulator, ToxT, and modulating its activity. FadR is a transcription factor that coordinately controls the pathways of FA degradation and biosynthesis in enteric bacteria. This study identifies a new link between FA metabolism and virulence in the El Tor biotype by showing that FadR influences both the transcription and posttranslational regulation of the master virulence regulator ToxT by two distinct mechanisms.

scholarly journals The Cyclic Dipeptide Cyclo(Phe-Pro) Inhibits Cholera Toxin and Toxin-Coregulated Pilus Production in O1 El Tor Vibrio cholerae

2010 ◽  
Vol 192 (14) ◽  
pp. 3829-3832 ◽  
Author(s):  
Xiaowen R. Bina ◽  
James E. Bina
Keyword(s):  
Cholera Toxin ◽  
Vibrio Cholerae ◽  
Virulence Factors ◽  
Virulence Gene ◽  
Cyclic Dipeptide ◽  
Present Evidence ◽  
Toxin Coregulated Pilus ◽  
El Tor ◽  
Virulence Regulator

ABSTRACT Cyclo(Phe-Pro) is a cyclic dipeptide produced by multiple Vibrio species. In this work, we present evidence that cyclo(Phe-Pro) inhibits the production of the virulence factors cholera toxin (CT) and toxin-coregulated pilus (TCP) in O1 El Tor Vibrio cholerae strain N16961 during growth under virulence gene-inducing conditions. The cyclo(Phe-Pro) inhibition of CT and TCP production correlated with reduced transcription of the virulence regulator tcpPH and was alleviated by overexpression of tcpPH.

scholarly journals Differential Transcription of the tcpPHOperon Confers Biotype-Specific Control of the Vibrio cholerae ToxR Virulence Regulon

1999 ◽  
Vol 67 (10) ◽  
pp. 5117-5123 ◽  
Author(s):  
Yvette M. Murley ◽  
Patricia A. Carroll ◽  
Karen Skorupski ◽  
Ronald K. Taylor ◽  
Stephen B. Calderwood
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Virulence Genes ◽  
Virulence Gene ◽  
Environmental Signals ◽  
Virulence Gene Expression ◽  
Response To Temperature ◽  
El Tor ◽  
Differential Transcription

ABSTRACT Epidemic strains of Vibrio cholerae O1 are divided into two biotypes, classical and El Tor. In both biotypes, regulation of virulence gene expression depends on a cascade in which ToxR activates expression of ToxT, and ToxT activates expression of cholera toxin and other virulence genes. In the classical biotype, maximal expression of this ToxR regulon in vitro occurs at 30°C at pH 6.5 (ToxR-inducing conditions), whereas in the El Tor biotype, production of these virulence genes only occurs under very limited conditions and not in response to temperature and pH; this difference between biotypes is mediated at the level of toxT transcription. In the classical biotype, two other proteins, TcpP and TcpH, are needed for maximal toxT transcription. Transcription oftcpPH in the classical biotype is regulated by pH and temperature independently of ToxR or ToxT, suggesting that TcpP and TcpH couple environmental signals to transcription of toxT. In this study, we show a near absence of tcpPH message in the El Tor biotype under ToxR-inducing conditions of temperature and pH. However, once expressed, El Tor TcpP and TcpH appear to be as effective as classical TcpP and TcpH in activating toxTtranscription. These results suggest that differences in regulation of virulence gene expression between the biotypes of V. cholerae primarily result from differences in expression oftcpPH message in response to environmental signals. We present an updated model for control of the ToxR virulence regulon inV. cholerae.

scholarly journals Requirements for Vibrio cholerae HapR Binding and Transcriptional Repression at the hapR Promoter Are Distinct from Those at the aphA Promoter

2005 ◽  
Vol 187 (9) ◽  
pp. 3013-3019 ◽  
Author(s):  
Wei Lin ◽  
Gabriela Kovacikova ◽  
Karen Skorupski
Keyword(s):  
Binding Site ◽  
Vibrio Cholerae ◽  
Cell Density ◽  
Transcriptional Repression ◽  
High Cell Density ◽  
Virulence Gene ◽  
High Cell ◽  
Mobility Shift ◽  
Virulence Gene Expression ◽  
Gel Mobility Shift

ABSTRACT Virulence gene expression in certain strains of Vibrio cholerae is regulated in response to cell density by a quorum-sensing cascade that influences the levels of the LuxR homolog HapR through small regulatory RNAs that control the stability of its message. At high cell density, HapR represses the expression of the gene encoding the virulence gene activator AphA by binding to a site between −85 and −58 in the aphA promoter. We show here that a second binding site for HapR lies within the hapR promoter from which it functions to repress its own transcription. This site, as determined by gel mobility shift assay and DNaseI footprinting, is located between +8 and +36 from the transcriptional start and is not strongly conserved with the site at the aphA promoter. At low cell density, when the expression of a transcriptional hapR-lacZ fusion was low, no autorepression was observed. However, at high cell density, when the expression of the hapR-lacZ fusion was approximately 15-fold higher, the presence of HapR reduced its expression. Introduction of a single base pair change within the binding site at +18 prevented HapR binding in gel mobility shift assays. In the absence of HapR, this mutation did not significantly influence the expression of the hapR promoter, but in its presence, the expression of the promoter was increased at high cell density. These results indicate that HapR autorepresses from a single binding site in the hapR promoter and suggest a model for the temporal regulation of its expression as its intracellular levels increase.

Variation in epitopes of the B subunit of Vibrio cholerae non-O1 and Vibrio mimicus cholera toxins

1990 ◽  
Vol 36 (6) ◽  
pp. 409-413 ◽  
Author(s):  
Mark L. Tamplin ◽  
Reema Jalali ◽  
Mohammed K. Ahmed ◽  
Rita R. Colwell
Keyword(s):  
Monoclonal Antibody ◽  
Monoclonal Antibodies ◽  
Binding Site ◽  
Cholera Toxin ◽  
Vibrio Cholerae ◽  
B Subunit ◽  
Vibrio Mimicus ◽  
Vibrio Cholerae O1 ◽  
El Tor ◽  
Reaction Patterns

Monoclonal antibodies reacting with the B subunit of Vibrio cholerae O1 strain 569B cholera toxin (CT-B) were used to identify unique and common epitopes of V. cholerae non-O1 and Vibrio mimicus CT-B. Vibrio cholerae non-O1 strains produced CT-B showing three monoclonal antibody reaction patterns (epitypes), which corresponded with epitypes described previously for V. cholerae O1 classical biotype CT-B (CT1), El Tor biotype CT-B (CT2), and a unique V. cholerae non-O1 CT-B (CT3), which lacked an epitope located in or near the GM1 ganglioside binding site of 569B CT-B. Vibrio mimicus CT-B was immunologically indistinguishable from 569B CT-B. These and previous results define six epitopes on 569B CT-B, and a fourth epitope in or near the GM1 ganglioside binding site. Key words: cholera toxin, epitopes, monoclonal antibodies.

scholarly journals Differences in Gene Expression between the Classical and El Tor Biotypes of Vibrio cholerae O1

2006 ◽  
Vol 74 (6) ◽  
pp. 3633-3642 ◽  
Author(s):  
Sinem Beyhan ◽  
Anna D. Tischler ◽  
Andrew Camilli ◽  
Fitnat H. Yildiz
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Deletion Mutant ◽  
Large Fraction ◽  
Expression Patterns ◽  
Virulence Gene ◽  
Differentially Expressed ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
El Tor

ABSTRACT Differences in whole-genome expression patterns between the classical and El Tor biotypes of Vibrio cholerae O1 were determined under conditions that induce virulence gene expression in the classical biotype. A total of 524 genes (13.5% of the genome) were found to be differentially expressed in the two biotypes. The expression of genes encoding proteins required for biofilm formation, chemotaxis, and transport of amino acids, peptides, and iron was higher in the El Tor biotype. These gene expression differences may contribute to the enhanced survival capacity of the El Tor biotype in environmental reservoirs. The expression of genes encoding virulence factors was higher in the classical than in the El Tor biotype. In addition, the vieSAB genes, which were originally identified as regulators of ctxA transcription, were expressed at a fivefold higher level in the classical biotype. We determined the VieA regulon in both biotypes by transcriptome comparison of wild-type and vieA deletion mutant strains. VieA predominantly regulates gene expression in the classical biotype; 401 genes (10.3% of the genome), including those encoding proteins required for virulence, exopolysaccharide biosynthesis, and flagellum production as well as those regulated by σE, are differentially expressed in the classical vieA deletion mutant. In contrast, only five genes were regulated by VieA in the El Tor biotype. A large fraction (20.8%) of the genes that are differentially expressed in the classical versus the El Tor biotype are controlled by VieA in the classical biotype. Thus, VieA is a major regulator of genes in the classical biotype under virulence gene-inducing conditions.

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