scholarly journals The Virulence Activator AphA Links Quorum Sensing to Pathogenesis and Physiology in Vibrio cholerae by Repressing the Expression of a Penicillin Amidase Gene on the Small Chromosome

2003 ◽  
Vol 185 (16) ◽  
pp. 4825-4836 ◽  
Author(s):  
Gabriela Kovacikova ◽  
Wei Lin ◽  
Karen Skorupski
Keyword(s):  
Quorum Sensing ◽  
Vibrio Cholerae ◽  
Cell Density ◽  
Transcriptional Activation ◽  
Small Chromosome ◽  
Site Directed Mutagenesis ◽  
Base Pairs ◽  
Penicillin Amidase ◽  
Expression Site ◽  
Dyad Symmetry

ABSTRACT Activation of the tcpPH promoter on the Vibrio pathogenicity island by AphA and AphB initiates the Vibrio cholerae virulence cascade and is regulated by quorum sensing through the repressive action of HapR on aphA expression. To further understand how the chromosomally encoded AphA protein activates tcpPH expression, site-directed mutagenesis was used to identify the base pairs critical for AphA binding and transcriptional activation. This analysis revealed a region of partial dyad symmetry, TATGCA-N6-TNCNNA, that is important for both of these activities. Searching the V. cholerae genome for this binding site permitted the identification of a second one upstream of a penicillin V amidase (PVA) gene on the small chromosome. AphA binds to and footprints this site, which overlaps the pva transcriptional start, consistent with its role as a repressor at this promoter. Since aphA expression is under quorum-sensing control, the response regulators LuxO and HapR also influence pva expression. Thus, pva is repressed at low cell density when AphA levels are high, and it is derepressed at high cell density when AphA levels are reduced. Penicillin amidases are thought to function as scavengers for phenylacetylated compounds in the nonparasitic environment. That AphA oppositely regulates the expression of pva from that of virulence, together with the observation that PVA does not play a role in virulence, suggests that these activities are coordinated to serve V. cholerae in different biological niches.

scholarly journals Quorum Sensing Controls Biofilm Formation in Vibrio cholerae through Modulation of Cyclic Di-GMP Levels and Repression of vpsT

2008 ◽  
Vol 190 (7) ◽  
pp. 2527-2536 ◽  
Author(s):  
Christopher M. Waters ◽  
Wenyun Lu ◽  
Joshua D. Rabinowitz ◽  
Bonnie L. Bassler
Keyword(s):  
Quorum Sensing ◽  
Vibrio Cholerae ◽  
Cell Density ◽  
Biofilm Formation ◽  
High Cell Density ◽  
High Cell ◽  
Chemical Signaling ◽  
Signaling Systems ◽  
Genes Encoding ◽  
Low Cell Density

ABSTRACT Two chemical signaling systems, quorum sensing (QS) and 3′,5′-cyclic diguanylic acid (c-di-GMP), reciprocally control biofilm formation in Vibrio cholerae. QS is the process by which bacteria communicate via the secretion and detection of autoinducers, and in V. cholerae, QS represses biofilm formation. c-di-GMP is an intracellular second messenger that contains information regarding local environmental conditions, and in V. cholerae, c-di-GMP activates biofilm formation. Here we show that HapR, a major regulator of QS, represses biofilm formation in V. cholerae through two distinct mechanisms. HapR controls the transcription of 14 genes encoding a group of proteins that synthesize and degrade c-di-GMP. The net effect of this transcriptional program is a reduction in cellular c-di-GMP levels at high cell density and, consequently, a decrease in biofilm formation. Increasing the c-di-GMP concentration at high cell density to the level present in the low-cell-density QS state restores biofilm formation, showing that c-di-GMP is epistatic to QS in the control of biofilm formation in V. cholerae. In addition, HapR binds to and directly represses the expression of the biofilm transcriptional activator, vpsT. Together, our results suggest that V. cholerae integrates information about the vicinal bacterial community contained in extracellular QS autoinducers with the intracellular environmental information encoded in c-di-GMP to control biofilm formation.

The intra-genus and inter-species quorum-sensing autoinducers exert distinct control over Vibrio cholerae biofilm formation and dispersal

2019 ◽  
Author(s):  
Andrew A. Bridges ◽  
Bonnie L. Bassler
Keyword(s):  
Quorum Sensing ◽  
Vibrio Cholerae ◽  
Cell Density ◽  
Biofilm Formation ◽  
Specific Information ◽  
High Cell ◽  
Coincidence Detector ◽  
Sensing System ◽  
Quorum Sensing System ◽  
Cell Densities

AbstractVibrio cholerae possesses multiple quorum-sensing systems that control virulence and biofilm formation among other traits. At low cell densities, when quorum-sensing autoinducers are absent, V. cholerae forms biofilms. At high cell densities, when autoinducers have accumulated, biofilm formation is repressed and dispersal occurs. Here, we focus on the roles of two well-characterized quorum-sensing autoinducers that function in parallel. One autoinducer, called CAI-1, is used to measure vibrio abundance, and the other autoinducer, called AI-2, is a broadly-made universal autoinducer that is presumed to enable V. cholerae to assess the total bacterial cell density of the vicinal community. The two V. cholerae autoinducers funnel information into a shared signal relay pathway. This feature of the quorum-sensing system architecture has made it difficult to understand how specific information can be extracted from each autoinducer, how the autoinducers might drive distinct output behaviors, and in turn, how the bacteria use quorum sensing to distinguish self from other in bacterial communities. We develop a live-cell biofilm formation and dispersal assay that allows examination of the individual and combined roles of the two autoinducers in controlling V. cholerae behavior. We show that the quorum-sensing system works as a coincidence detector in which both autoinducers must be present simultaneously for repression of biofilm formation to occur. Within that context, the CAI-1 quorum-sensing pathway is activated when only a few V. cholerae cells are present, whereas the AI-2 pathway is activated only at much higher cell density. The consequence of this asymmetry is that exogenous sources of AI-2, but not CAI-1, contribute to satisfying the coincidence detector to repress biofilm formation and promote dispersal. We propose that V. cholerae uses CAI-1 to verify that some of its kin are present before committing to the high-cell-density quorum-sensing mode, but it is, in fact, the universal autoinducer AI-2, that sets the pace of the V. cholerae quorum-sensing program. This first report of unique roles for the different V. cholerae autoinducers suggests that detection of self fosters a distinct outcome from detection of other.

scholarly journals The quorum sensing transcription factor AphA directly regulates natural competence in Vibrio cholerae

2019 ◽  
Author(s):  
James R. J. Haycocks ◽  
Gemma Z. L. Warren ◽  
Lucas M. Walker ◽  
Jennifer L. Chlebek ◽  
Triana N. Dalia ◽  
...  
Keyword(s):  
Dna Binding ◽  
Quorum Sensing ◽  
Vibrio Cholerae ◽  
Cell Density ◽  
High Cell Density ◽  
Financial Burden ◽  
Ectopic Expression ◽  
Dna Uptake ◽  
High Cell ◽  
Natural Competence

ABSTRACTMany bacteria use population density to control gene expression via quorum sensing. In Vibrio cholerae, quorum sensing coordinates virulence, biofilm formation, and DNA uptake by natural competence. The transcription factors AphA and HapR, expressed at low- and high-cell density respectively, play a key role. In particular, AphA triggers the entire virulence cascade upon host colonisation. In this work we have mapped genome-wide DNA binding by AphA. We show that AphA is versatile, exhibiting distinct modes of DNA binding and promoter regulation. Unexpectedly, whilst HapR is known to induce natural competence, we demonstrate that AphA also intervenes. Most notably, AphA is a direct repressor of tfoX, the master activator of competence. Hence, production of AphA markedly suppressed DNA uptake; an effect largely circumvented by ectopic expression of tfoX. Our observations suggest dual regulation of competence. At low cell density AphA is a master repressor whilst HapR activates the process at high cell density. Thus, we provide deep mechanistic insight into the role of AphA and highlight how V. cholerae utilises this regulator for diverse purposes.AUTHOR SUMMARYCholera remains a devastating diarrhoeal disease responsible for millions of cases, thousands of deaths, and a $3 billion financial burden every year. Although notorious for causing human disease, the microorganism responsible for cholera is predominantly a resident of aquatic environments. Here, the organism survives in densely packed communities on the surfaces of crustaceans. Remarkably, in this situation, the microbe can feast on neighbouring cells and acquire their DNA. This provides a useful food source and an opportunity to obtain new genetic information. In this paper, we have investigated how acquisition of DNA from the local environment is regulated. We show that a “switch” within the microbial cell, known to activate disease processes in the human host, also controls DNA uptake. Our results explain why DNA scavenging only occurs in suitable environments and illustrates how interactions between common regulatory switches affords precise control of microbial behaviours.

scholarly journals The Vibrio cholerae Quorum-Sensing Protein VqmA Integrates Cell Density, Environmental, and Host-Derived Cues into the Control of Virulence

mBio ◽  
2020 ◽  
Vol 11 (4) ◽  
Author(s):  
Ameya A. Mashruwala ◽  
Bonnie L. Bassler
Keyword(s):  
Small Intestine ◽  
Quorum Sensing ◽  
Vibrio Cholerae ◽  
Cell Density ◽  
Chemical Communication ◽  
Bile Salts ◽  
Anaerobic Growth ◽  
Signal Molecules ◽  
Content Type ◽  
Collective Behaviors

ABSTRACT Quorum sensing is a chemical communication process in which bacteria use the production, release, and detection of signal molecules called autoinducers to orchestrate collective behaviors. The human pathogen Vibrio cholerae requires quorum sensing to infect the small intestine. There, V. cholerae encounters the absence of oxygen and the presence of bile salts. We show that these two stimuli differentially affect quorum-sensing function and, in turn, V. cholerae pathogenicity. First, during anaerobic growth, V. cholerae does not produce the CAI-1 autoinducer, while it continues to produce the DPO autoinducer, suggesting that CAI-1 may encode information specific to the aerobic lifestyle of V. cholerae. Second, the quorum-sensing receptor-transcription factor called VqmA, which detects the DPO autoinducer, also detects the lack of oxygen and the presence of bile salts. Detection occurs via oxygen-, bile salt-, and redox-responsive disulfide bonds that alter VqmA DNA binding activity. We propose that VqmA serves as an information processing hub that integrates quorum-sensing information, redox status, the presence or absence of oxygen, and host cues. In response to the information acquired through this mechanism, V. cholerae appropriately modulates its virulence output. IMPORTANCE Quorum sensing (QS) is a process of chemical communication that bacteria use to orchestrate collective behaviors. QS communication relies on chemical signal molecules called autoinducers. QS regulates virulence in Vibrio cholerae, the causative agent of the disease cholera. Transit into the human small intestine, the site of cholera infection, exposes V. cholerae to the host environment. In this study, we show that the combination of two stimuli encountered in the small intestine, the absence of oxygen and the presence of host-produced bile salts, impinge on V. cholerae QS function and, in turn, pathogenicity. We suggest that possessing a QS system that is responsive to multiple environmental, host, and cell density cues enables V. cholerae to fine-tune its virulence capacity in the human intestine.

scholarly journals Levels of the Secreted Vibrio cholerae Attachment Factor GbpA Are Modulated by Quorum-Sensing-Induced Proteolysis

2009 ◽  
Vol 191 (22) ◽  
pp. 6911-6917 ◽  
Author(s):  
Brooke A. Jude ◽  
Raquel M. Martinez ◽  
Karen Skorupski ◽  
Ronald K. Taylor
Keyword(s):  
Quorum Sensing ◽  
Vibrio Cholerae ◽  
Cell Density ◽  
Protein A ◽  
Etiologic Agent ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Secreted Proteases ◽  
Low Cell Density ◽  
Attachment Factor

ABSTRACT Vibrio cholerae is the etiologic agent of cholera in humans. Intestinal colonization occurs in a stepwise fashion, initiating with attachment to the small intestinal epithelium. This attachment is followed by expression of the toxin-coregulated pilus, microcolony formation, and cholera toxin (CT) production. We have recently characterized a secreted attachment factor, GlcNAc binding protein A (GbpA), which functions in attachment to environmental chitin sources as well as to intestinal substrates. Studies have been initiated to define the regulatory network involved in GbpA induction. At low cell density, GbpA was detected in the culture supernatant of all wild-type (WT) strains examined. In contrast, at high cell density, GbpA was undetectable in strains that produce HapR, the central regulator of the cell density-dependent quorum-sensing system of V. cholerae. HapR represses the expression of genes encoding regulators involved in V. cholerae virulence and activates the expression of genes encoding the secreted proteases HapA and PrtV. We show here that GbpA is degraded by HapA and PrtV in a time-dependent fashion. Consistent with this, ΔhapA ΔprtV strains attach to chitin beads more efficiently than either the WT or a ΔhapA ΔprtV ΔgbpA strain. These results suggest a model in which GbpA levels fluctuate in concert with the bacterial production of proteases in response to quorum-sensing signals. This could provide a mechanism for GbpA-mediated attachment to, and detachment from, surfaces in response to environmental cues.

scholarly journals Ethanolamine regulates CqsR quorum-sensing signaling inVibrio cholerae

2019 ◽  
Author(s):  
Samit Watve ◽  
Kelsey Barrasso ◽  
Sarah A. Jung ◽  
Kristen J. Davis ◽  
Lisa A. Hawver ◽  
...  
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Vibrio Cholerae ◽  
Cell Density ◽  
High Cell Density ◽  
Chemical Signals ◽  
Communication Process ◽  
Control Group ◽  
Dual Function ◽  
High Cell

ABSTRACTThe pathogen that causes cholera,Vibrio cholerae, uses the cell-cell communication process known as quorum sensing (QS) to regulate virulence factor production and biofilm formation in response to changes in population density and complexity. QS is mediated through the detection of extracellular chemical signals called autoinducers. Four histidine kinases, LuxPQ, CqsS, CqsR and VpsS, have been identified as receptors to activate the key QS regulator LuxO at low cell density. At high cell density, detection of autoinducers by these receptors leads to deactivation of LuxO, resulting in population-wide gene expression changes. While the cognate autoinducers that regulate the activity of CqsS and LuxQ are known, the signals that regulate CqsR have not been determined. Here we show that the common metabolite ethanolamine specifically interacts with the ligand-binding CACHE domain of CqsRin vitroand induces the high cell-density QS response through CqsR kinase inhibition inV. choleraecells. We also identified residues in the CqsR CACHE domain important for ethanolamine detection and signal transduction. Moreover, mutations disrupting endogenous ethanolamine production inV. choleraedelay the onset of, but do not abolish, the high cell-density QS gene expression. Finally, we demonstrate that modulation of CqsR QS response by ethanolamine occurs inside animal hosts. Our findings suggest thatV. choleraeuses CqsR as a dual-function receptor to integrate information from the self-made signals as well as exogenous ethanolamine as an environmental cue to modulate QS response.IMPORTANCEMany bacteria use quorum sensing to regulate cellular processes that are important for their survival and adaptation to different environments. Quorum sensing usually depends on the detection on chemical signals called autoinducers made endogenously by the bacteria. We show here ethanolamine, a common metabolite made by various bacteria and eukaryotes, can modulate the activity of one of the quorum-sensing receptors inVibrio cholerae, the etiological agent of the disease cholera. Our results raise the possibility thatV. choleraeor other quorum-sensing bacteria can combine environmental sensing and quorum sensing to control group behaviors.

scholarly journals Mechanism underlying autoinducer recognition in the Vibrio cholerae DPO-VqmA quorum-sensing pathway

2019 ◽  
Author(s):  
Xiuliang Huang ◽  
Olivia P. Duddy ◽  
Justin E. Silpe ◽  
Jon E. Paczkowski ◽  
Jianping Cong ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Vibrio Cholerae ◽  
Conformational Changes ◽  
Site Directed Mutagenesis ◽  
Communication Process ◽  
Linear Molecule ◽  
Gene Encoding ◽  
Collective Behaviors ◽  
Existing Structures ◽  
Extracellular Signaling

ABSTRACTQuorum sensing is a bacterial communication process whereby bacteria produce, release and detect the accumulation of extracellular signaling molecules called autoinducers to coordinate collective behaviors. In Vibrio cholerae, the quorum-sensing autoinducer, DPO (3,5-dimethyl-pyrazin-2-ol), binds the receptor-transcription factor, VqmA. In response, the DPO-VqmA complex activates transcription of the vqmR gene encoding the VqmR small RNA. VqmR represses genes required for biofilm formation and virulence factor production. Here, we show that VqmA has DPO-dependent and DPO-independent activity. We solved the DPO-VqmA crystal structure and compared it to existing structures to understand the conformational changes the protein undergoes upon DNA binding. Analysis of DPO analogs reveals that a hydroxyl or carbonyl group at the 2’ position is critical for binding. The proposed DPO precursor, a linear molecule, Ala-AA (N-alanyl-aminoacetone), also binds and activates VqmA. DPO and Ala-AA occupy the same binding site as judged by site-directed mutagenesis and competitive ligand binding analyses.

scholarly journals The VarS/VarA two-component system modulates the activity of the Vibrio cholerae quorum-sensing transcriptional regulator HapR

Microbiology ◽  
2011 ◽  
Vol 157 (6) ◽  
pp. 1620-1628 ◽  
Author(s):  
Amy M. Tsou ◽  
Zhi Liu ◽  
Tao Cai ◽  
Jun Zhu
Keyword(s):  
Quorum Sensing ◽  
Vibrio Cholerae ◽  
Cell Density ◽  
Transcriptional Regulator ◽  
Nutrient Status ◽  
Two Component System ◽  
Protein Activity ◽  
Component System ◽  
Its Gene ◽  
Two Component

The human pathogen Vibrio cholerae uses quorum sensing to regulate the expression of a number of phenotypes, including virulence factor production, in response to changes in cell density. It produces small molecules called autoinducers that increase in concentration as cell density increases, and these autoinducers bind to membrane sensors once they reach a certain threshold. This binding leads to signalling through a downstream phosphorelay pathway to alter the expression of the transcriptional regulator HapR. Previously, it was shown that the VarS/VarA two-component system acts on a component of the phosphorelay pathway upstream of HapR to regulate HapR expression levels. Here, we show that in addition to this mechanism of regulation, VarS and VarA also indirectly modulate HapR protein activity. This modulation is mediated by the small RNA CsrB but is independent of the known quorum-sensing system that links the autoinducers to HapR. Thus, the VarS/VarA two-component system intersects with the quorum-sensing network at two levels. In both cases, the effect of VarS and VarA on quorum sensing is dependent on the Csr small RNAs, which regulate carbon metabolism, suggesting that V. cholerae may integrate nutrient status and cell density sensory inputs to tailor its gene expression profile more precisely to surrounding conditions.

scholarly journals Transcriptional Regulation of Vibrio cholerae Hemagglutinin/Protease by the Cyclic AMP Receptor Protein and RpoS

2004 ◽  
Vol 186 (19) ◽  
pp. 6374-6382 ◽  
Author(s):  
Anisia J. Silva ◽  
Jorge A. Benitez
Keyword(s):  
Quorum Sensing ◽  
Cyclic Amp ◽  
Vibrio Cholerae ◽  
Transcriptional Activation ◽  
Response Regulator ◽  
Stringent Response ◽  
Receptor Protein ◽  
Mobility Shift ◽  
Deceleration Phase ◽  
Camp Receptor

ABSTRACT Vibrio cholerae secretes a Zn-dependent metalloprotease, hemagglutinin/protease (HA/protease), which is encoded by hapA and displays a broad range of potentially pathogenic activities. Production of HA/protease requires transcriptional activation by the quorum-sensing regulator HapR. In this study we demonstrate that transcription of hapA is growth phase dependent and specifically activated in the deceleration and stationary growth phases. Addition of glucose in these phases repressed hapA transcription by inducing V. cholerae to resume exponential growth, which in turn diminished the expression of a rpoS-lacZ transcriptional fusion. Contrary to a previous observation, we demonstrate that transcription of hapA requires the rpoS-encoded σs factor. The cyclic AMP (cAMP) receptor protein (CRP) strongly enhanced hapA transcription in the deceleration phase. Analysis of rpoS and hapR mRNA in isogenic CRP+ and CRP− strains suggested that CRP enhances the transcription of rpoS and hapR. Analysis of strains containing hapR-lacZ and hapA-lacZ fusions confirmed that hapA is transcribed in response to concurrent quorum-sensing and nutrient limitation stimuli. Mutations inactivating the stringent response regulator RelA and the HapR-controlled AphA regulator did not affect HA/protease expression. Electrophoretic mobility shift experiments showed that pure cAMP-CRP and HapR alone do not bind the hapA promoter. This result suggests that HapR activation of hapA differs from its interaction with the aphA promoter and could involve additional factors.

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