Quorum sensing influences growth and photosynthetic membrane production in high-cell-density cultivations of Rhodospirillum rubrum

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.

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

10.1101/732818 ◽

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.

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Quorum sensing regulates the transcription of lateral flagellar genes in Vibrio parahaemolyticus

Future Microbiology ◽

10.2217/fmb-2019-0048 ◽

2019 ◽

Vol 14 (12) ◽

pp. 1043-1053 ◽

Cited By ~ 5

Author(s):

Renfei Lu ◽

Hao Tang ◽

Yue Qiu ◽

Wenhui Yang ◽

Huiying Yang ◽

...

Keyword(s):

Quorum Sensing ◽

Cell Density ◽

Vibrio Parahaemolyticus ◽

High Cell Density ◽

High Cell ◽

Regulatory Effect ◽

Swarming Motility ◽

Dnase I Footprinting ◽

Regulation Mechanisms ◽

Low Cell Density

Aim: Investigation of the lateral flagellar (Laf) genes transcription by the quorum sensing (QS) regulators AphA and OpaR in Vibrio parahaemolyticus. Materials & methods: Regulation mechanisms were assessed by combined utilization of swarming motility assay, qPCR, LacZ fusion, EMSA and DNase I footprinting. Results: AphA and OpaR oppositely regulate swarming motility and Laf genes. At high cell density, OpaR bound to the regulatory regions of motY-lafK-fliEFGHIJ, fliMNPQR-flhBA, fliDSTKLA-motAB and lafA to repress their transcription. At low cell density, AphA indirectly activated their transcription. Conclusion: OpaR repression of swarming motility was via its direct repression of Laf genes, while AphA exerted its regulatory effect on swarming motility through unknown regulator(s).

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Abstract 4117: Defective quorum sensing in Ph+ ALL and identification of diffusible factors secreted by cells growing at high cell density.

10.1158/1538-7445.am2013-4117 ◽

2013 ◽

Cited By ~ 2

Author(s):

Sapan J. Patel ◽

Dao Su ◽

Bayard Clarkson

Keyword(s):

Quorum Sensing ◽

Cell Density ◽

High Cell Density ◽

High Cell

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The Fur-Iron Complex Modulates Expression of the Quorum-Sensing Master Regulator, SmcR, To Control Expression of Virulence Factors in Vibrio vulnificus

Infection and Immunity ◽

10.1128/iai.00375-13 ◽

2013 ◽

Vol 81 (8) ◽

pp. 2888-2898 ◽

Cited By ~ 22

Author(s):

In Hwang Kim ◽

Yancheng Wen ◽

Jee-Soo Son ◽

Kyu-Ho Lee ◽

Kun-Soo Kim

Keyword(s):

Quorum Sensing ◽

Cell Density ◽

Virulence Factors ◽

Vibrio Vulnificus ◽

High Cell Density ◽

Iron Complex ◽

High Cell ◽

Mobility Shift ◽

Master Regulator ◽

Content Type

ABSTRACTThe genevvpE, encoding the virulence factor elastase, is a member of the quorum-sensing regulon inVibrio vulnificusand displays enhanced expression at high cell density. We observed that this gene was repressed under iron-rich conditions and that the repression was due to a Fur (ferricuptakeregulator)-dependent repression ofsmcR, a gene encoding a quorum-sensing master regulator with similarity toluxRinVibrio harveyi. A gel mobility shift assay and a footprinting experiment demonstrated that the Fur-iron complex binds directly to two regions upstream ofsmcR(−82 to −36 and −2 to +27, with respect to the transcription start site) with differing affinities. However, binding of the Fur-iron complex is reversible enough to allow expression ofsmcRto be induced by quorum sensing at high cell density under iron-rich conditions. Under iron-limiting conditions, Fur fails to bind either region and the expression ofsmcRis regulated solely by quorum sensing. These results suggest that two biologically important environmental signals, iron and quorum sensing, converge to direct the expression ofsmcR, which then coordinates the expression of virulence factors.

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Ethanolamine regulates CqsR quorum-sensing signaling inVibrio cholerae

10.1101/589390 ◽

2019 ◽

Cited By ~ 3

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.

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Control of the Type 3 Secretion System in Vibrio harveyi by Quorum Sensing through Repression of ExsA

Applied and Environmental Microbiology ◽

10.1128/aem.00886-10 ◽

2010 ◽

Vol 76 (15) ◽

pp. 4996-5004 ◽

Cited By ~ 25

Author(s):

Christopher M. Waters ◽

Julie T. Wu ◽

Meghan E. Ramsey ◽

Rebecca C. Harris ◽

Bonnie L. Bassler

Keyword(s):

Quorum Sensing ◽

Cell Density ◽

Target Genes ◽

High Cell Density ◽

Vibrio Harveyi ◽

Secretion System ◽

High Cell ◽

Type 3 Secretion System ◽

Type 3 ◽

Low Cell Density

ABSTRACT The type 3 secretion system (T3SS) genes of Vibrio harveyi are activated at low cell density and repressed at high cell density by quorum sensing (QS). Repression requires LuxR, the master transcriptional regulator of QS-controlled genes. Here, we determine the mechanism underlying the LuxR repression of the T3SS system. Using a fluorescence-based cell sorting approach, we isolated V. harveyi mutants that are unable to express T3SS genes at low cell density and identified two mutations in the V. harveyi exsBA operon. While LuxR directly represses the expression of exsBA, complementation and epistasis analyses reveal that it is the repression of exsA expression, but not exsB expression, that is responsible for the QS-mediated repression of T3SS genes at high cell density. The present work further defines the genes in the V. harveyi QS regulon and elucidates a mechanism demonstrating how multiple regulators can be linked in series to direct the expression of QS target genes specifically at low or high cell density.

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Role for Cell Density in Antifungal Drug Resistance in Candida albicans Biofilms

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01237-06 ◽

2007 ◽

Vol 51 (7) ◽

pp. 2454-2463 ◽

Cited By ~ 112

Author(s):

Palani Perumal ◽

Satish Mekala ◽

W. LaJean Chaffin

Keyword(s):

Candida Albicans ◽

Quorum Sensing ◽

Cell Density ◽

High Cell Density ◽

Yeast Cells ◽

Drug Efflux ◽

High Cell ◽

Phenotypic Resistance ◽

Drug Efflux Pumps ◽

Low Cell Density

ABSTRACT Biofilms of Candida albicans are less susceptible to many antifungal drugs than are planktonic yeast cells. We investigated the contribution of cell density to biofilm phenotypic resistance. Planktonic yeast cells in RPMI 1640 were susceptible to azole-class drugs, amphotericin B, and caspofungin at 1 × 103 cells/ml (standard conditions) using the XTT [2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide sodium salt] assay. As reported by others, as the cell concentration increased to 1 × 108 cells/ml, resistance was observed with 10- to 20-fold-greater MICs. Biofilms that formed in microtiter plate wells, like high-density planktonic organisms, were resistant to drugs. When biofilms were resuspended before testing, phenotypic resistance remained, but organisms, when diluted to 1 × 103 cells/ml, were susceptible. Drug-containing medium recovered from high-cell-density tests inhibited low-cell-density organisms. A fluconazole-resistant strain showed greater resistance at high planktonic cell density, in biofilm, and in resuspended biofilm than did low-density planktonic or biofilm organisms. A strain lacking drug efflux pumps CDR1, CDR2, and MDR1, while susceptible at a low azole concentration, was resistant at high cell density and in biofilm. A strain lacking CHK1 that fails to respond to the quorum-sensing molecule farnesol had the same response as did the wild type. FK506, reported to abrogate tolerance to azole drugs at low cell density, had no effect on tolerance at high cell density and in biofilm. These observations suggested that cell density has a role in the phenotypic resistance of biofilm, that neither the drug efflux pumps tested nor quorum sensing through Chk1p contributes to resistance, and that azole drug tolerance at high cell density differs mechanistically from tolerance at low cell density.

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Quorum Sensing Coordinates Cooperative Expression of Pyruvate Metabolism Genes To Maintain a Sustainable Environment for Population Stability

mBio ◽

10.1128/mbio.01863-16 ◽

2016 ◽

Vol 7 (6) ◽

Cited By ~ 22

Author(s):

Lisa A. Hawver ◽

Jennifer M. Giulietti ◽

James D. Baleja ◽

Wai-Leung Ng

Keyword(s):

Quorum Sensing ◽

Cell Density ◽

Common Good ◽

High Cell Density ◽

Carbon Sources ◽

Population Stability ◽

High Cell ◽

Sustainable Environment ◽

The Common ◽

Low Cell Density

ABSTRACTQuorum sensing (QS) is a microbial cell-cell communication system that regulates gene expression in response to population density to coordinate collective behaviors. Yet, the role of QS in resolving the stresses caused by the accumulation of toxic metabolic by-products at high cell density is not well defined. In response to cell density, QS could be involved in reprogramming of the metabolic network to maintain population stability. Using unbiased metabolomics, we discovered thatVibrio choleraemutants genetically locked in a low cell density (LCD) QS state are unable to alter the pyruvate flux to convert fermentable carbon sources into neutral acetoin and 2,3-butanediol molecules to offset organic acid production. As a consequence, LCD-locked QS mutants rapidly lose viability when grown with fermentable carbon sources. This key metabolic switch relies on the QS-regulated small RNAs Qrr1-4 but is independent of known QS regulators AphA and HapR. Qrr1-4 dictate pyruvate flux by translational repression of the enzyme AlsS, which carries out the first step in acetoin and 2,3-butanediol biosynthesis. Consistent with the idea that QS facilitates the expression of a common trait in the population, AlsS needs to be expressed cooperatively in a group of cells. Heterogeneous populations with high percentages of cells not expressing AlsS are unstable. All of the cells, regardless of their respective QS states, succumb to stresses caused by toxic by-product accumulation. Our results indicate that the ability of the bacteria to cooperatively control metabolic flux through QS is critical in maintaining a sustainable environment and overall population stability.IMPORTANCEOur work reveals a novel role forVibrio choleraequorum sensing (QS) in relieving the stresses caused by toxic metabolite accumulation when the population becomes crowded through metabolic reprogramming. QS enablesV. choleraeswitching from a low cell density energy-generating metabolism that is beneficial to individuals at the expense of the environment to a high cell density mode that preserves environmental habitability by sacrificing individual fitness. This cooperative switch provides a stable environment as the common good in maintaining the stability of the community. However, the common good can be exploited by uncooperative mutants that pollute the environment, causing population collapse. Our findings provide insights into the metabolic stress response of a major human pathogen, with implications for our understanding of microbial social biology and cooperation from an ecological and evolutionary perspective.

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Quorum Sensing-Mediated and Growth Phase-Dependent Regulation of Metabolic Pathways in Hafnia alvei H4

Frontiers in Microbiology ◽

10.3389/fmicb.2021.567942 ◽

2021 ◽

Vol 12 ◽

Author(s):

Congyang Yan ◽

Xue Li ◽

Gongliang Zhang ◽

Yaolei Zhu ◽

Jingran Bi ◽

...

Keyword(s):

Quorum Sensing ◽

Cell Density ◽

Growth Phase ◽

Metabolic Pathways ◽

High Cell Density ◽

Dependent Manner ◽

High Cell ◽

Wild Type ◽

Hafnia Alvei ◽

Density Dependent

Quorum sensing (QS) is a widespread regulatory mechanism in bacteria used to coordinate target gene expression with cell density. Thus far, little is known about the regulatory relationship between QS and cell density in terms of metabolic pathways in Hafnia alvei H4. In this study, transcriptomics analysis was performed under two conditions to address this question. The comparative transcriptome of H. alvei H4 wild-type at high cell density (OD600 = 1.7) relative to low cell density (OD600 = 0.3) was considered as growth phase-dependent manner (GPDM), and the transcriptome profile of luxI/R deletion mutant (ΔluxIR) compared to the wild-type was considered as QS-mediated regulation. In all, we identified 206 differentially expressed genes (DEGs) mainly presented in chemotaxis, TCA cycle, two-component system, ABC transporters and pyruvate metabolism, co-regulated by the both density-dependent regulation, and the results were validated by qPCR and swimming phenotypic assays. Aside from the co-regulated DEGs, we also found that 59 DEGs, mediated by density-independent QS, function in pentose phosphate and histidine metabolism and that 2084 cell-density-dependent DEGs involved in glycolysis/gluconeogenesis and phenylalanine metabolism were influenced only by GPDM from significantly enriched analysis of transcriptome data. The findings provided new information about the interplay between two density-dependent metabolic regulation, which could assist with the formulation of control strategies for this opportunistic pathogen, especially at high cell density.

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