scholarly journals PldB, a Putative Phospholipase D Homologue in Dictyostelium discoideum Mediates Quorum Sensing during Development

2005 ◽  
Vol 4 (4) ◽  
pp. 694-702 ◽  
Author(s):  
Yi Chen ◽  
Vanessa Rodrick ◽  
Yi Yan ◽  
Derrick Brazill
Keyword(s):  
Quorum Sensing ◽  
Cell Density ◽  
Dictyostelium Discoideum ◽  
Phospholipase D ◽  
Unicellular Eukaryote ◽  
Wild Type ◽  
Developmental Gene Expression ◽  
Gene Coding ◽  
Early Developmental ◽  
Low Cell Density

ABSTRACT Quorum sensing, also known as cell-density sensing in the unicellular eukaryote Dictyostelium discoideum, is required for efficient entry into the differentiation and development segment of its life cycle. Quorum sensing is accomplished by simultaneously secreting and sensing the glycoprotein Conditioned Medium Factor, or CMF. When the density of starving cells is high, CMF levels are high, which leads to aggregation followed by development. Here, we describe the role of pldB, a gene coding for a putative phospholipase D (PLD) homologue, in quorum sensing. We find that in submerged culture, adding butanol, an inhibitor of PLD-catalyzed phosphatidic acid production, allows cells to bypass the requirement for CMF mediated quorum sensing and aggregate at low cell density. Deletion of pldB mimics the presence of butanol, allowing cells to aggregate at low cell density. pldB − cells also initiate and finish aggregation rapidly. Analysis of early developmental gene expression in pldB − cells reveals that the cyclic AMP receptor cAR1 is expressed at higher levels earlier than in wild-type cells, which could explain the rapid aggregation phenotype. As would be predicted, cells overexpressing pldB are unable to aggregate even at high cell density. Adding CMF to these pldB − overexpressing cells does not rescue aggregation. Both of these phenotypes are cell autonomous, as mixing a small number of pldB − cells with wild-type cells does not cause the wild-type cells to behave like pldB − cells.

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.

scholarly journals CbfA, the C-Module DNA-Binding Factor, Plays an Essential Role in the Initiation of Dictyostelium discoideum Development

2004 ◽  
Vol 3 (5) ◽  
pp. 1349-1358 ◽  
Author(s):  
Thomas Winckler ◽  
Negin Iranfar ◽  
Peter Beck ◽  
Ingo Jennes ◽  
Oliver Siol ◽  
...  
Keyword(s):  
Dna Binding ◽  
Cell Density ◽  
Dictyostelium Discoideum ◽  
Ectopic Expression ◽  
Development Program ◽  
Cell Physiology ◽  
Dependent Manner ◽  
Wild Type ◽  
Gene Encoding ◽  
Multicellular Development

ABSTRACT We recently isolated from Dictyostelium discoideum cells a DNA-binding protein, CbfA, that interacts in vitro with a regulatory element in retrotransposon TRE5-A. We have generated a mutant strain that expresses CbfA at <5% of the wild-type level to characterize the consequences for D. discoideum cell physiology. We found that the multicellular development program leading to fruiting body formation is highly compromised in the mutant. The cells cannot aggregate and stay as a monolayer almost indefinitely. The cells respond properly to prestarvation conditions by expressing discoidin in a cell density-dependent manner. A genomewide microarray-assisted expression analysis combined with Northern blot analyses revealed a failure of CbfA-depleted cells to induce the gene encoding aggregation-specific adenylyl cyclase ACA and other genes required for cyclic AMP (cAMP) signal relay, which is necessary for aggregation and subsequent multicellular development. However, the cbfA mutant aggregated efficiently when mixed with as few as 5% wild-type cells. Moreover, pulsing cbfA mutant cells developing in suspension with nanomolar levels of cAMP resulted in induction of acaA and other early developmental genes. Although the response was less efficient and slower than in wild-type cells, it showed that cells depleted of CbfA are able to initiate development if given exogenous cAMP signals. Ectopic expression of the gene encoding the catalytic subunit of protein kinase A restored multicellular development of the mutant. We conclude that sensing of cell density and starvation are independent of CbfA, whereas CbfA is essential for the pattern of gene expression which establishes the genetic network leading to aggregation and multicellular development of D. discoideum.

scholarly journals Sociality in Escherichia coli: Enterochelin Is a Private Good at Low Cell Density and Can Be Shared at High Cell Density

2015 ◽  
Vol 197 (13) ◽  
pp. 2122-2128 ◽  
Author(s):  
Rebecca L. Scholz ◽  
E. Peter Greenberg
Keyword(s):  
Escherichia Coli ◽  
Cell Density ◽  
Iron Acquisition ◽  
Partial Privatization ◽  
High Cell ◽  
Wild Type ◽  
Content Type ◽  
Cell Densities ◽  
The Cost ◽  
Low Cell Density

ABSTRACTMany bacteria produce secreted iron chelators called siderophores, which can be shared among cells with specific siderophore uptake systems regardless of whether the cell produces siderophores. Sharing secreted products allows freeloading, where individuals use resources without bearing the cost of production. Here we show that theEscherichia colisiderophore enterochelin is not evenly shared between producers and nonproducers. Wild-typeEscherichia coligrows well in low-iron minimal medium, and an isogenic enterochelin synthesis mutant (ΔentF) grows very poorly. The enterochelin mutant grows well in low-iron medium supplemented with enterochelin. At high cell densities the ΔentFmutant can compete equally with the wild type in low-iron medium. At low cell densities the ΔentFmutant cannot compete. Furthermore, the growth rate of the wild type is unaffected by cell density. The wild type grows well in low-iron medium even at very low starting densities. Our experiments support a model where at least some enterochelin remains associated with the cells that produce it, and the cell-associated enterochelin enables iron acquisition even at very low cell density. Enterochelin that is not retained by producing cells at low density is lost to dilution. At high cell densities, cell-free enterochelin can accumulate and be shared by all cells in the group. Partial privatization is a solution to the problem of iron acquisition in low-iron, low-cell-density habitats. Cell-free enterochelin allows for iron scavenging at a distance at higher population densities. Our findings shed light on the conditions under which freeloaders might benefit from enterochelin uptake systems.IMPORTANCESociality in microbes has become a topic of great interest. One facet of sociality is the sharing of secreted products, such as the iron-scavenging siderophores. We present evidence that theEscherichia colisiderophore enterochelin is relatively inexpensive to produce and is partially privatized such that it can be efficiently shared only at high producer cell densities. At low cell densities, cell-free enterochelin is scarce and only enterochelin producers are able to grow in low-iron medium. Because freely shared products can be exploited by freeloaders, this partial privatization may help explain how enterochelin production is stabilized inE. coliand may provide insight into when enterochelin is available for freeloaders.

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

2019 ◽  
Vol 14 (12) ◽  
pp. 1043-1053 ◽  
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).

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

2010 ◽  
Vol 76 (15) ◽  
pp. 4996-5004 ◽  
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.

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

2007 ◽  
Vol 51 (7) ◽  
pp. 2454-2463 ◽  
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.

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

mBio ◽  
2016 ◽  
Vol 7 (6) ◽  
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.

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

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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