scholarly journals Quorum Sensing Determines the Choice of Antiphage Defense Strategy in Vibrio anguillarum

mBio ◽  
2015 ◽  
Vol 6 (3) ◽  
Author(s):  
Demeng Tan ◽  
Sine Lo Svenningsen ◽  
Mathias Middelboe
Keyword(s):  
Quorum Sensing ◽  
Cell Density ◽  
Defense Mechanisms ◽  
Vibrio Anguillarum ◽  
Phage Infection ◽  
Phage Resistance ◽  
Fish Pathogen ◽  
Content Type ◽  
Density State ◽  
Infection Pressure

ABSTRACTSelection for phage resistance is a key driver of bacterial diversity and evolution, and phage-host interactions may therefore have strong influence on the genetic and functional dynamics of bacterial communities. In this study, we found that an important, but so far largely overlooked, determinant of the outcome of phage-bacterial encounters in the fish pathogenVibrio anguillarumis bacterial cell-cell communication, known as quorum sensing. Specifically,V. anguillarumPF430-3 cells locked in the low-cell-density state (ΔvanTmutant) express high levels of the phage receptor OmpK, resulting in a high susceptibility to phage KVP40, but achieve protection from infection by enhanced biofilm formation. By contrast, cells locked in the high-cell-density state (ΔvanΟmutant) are almost completely unsusceptible due to quorum-sensing-mediated downregulation of OmpK expression. The phenotypes of the two quorum-sensing mutant strains are accurately reflected in the behavior of wild-typeV. anguillarum, which (i) displays increased OmpK expression in aggregated cells compared to free-living variants in the same culture, (ii) displays a clear inverse correlation betweenompKmRNA levels and the concentration ofN-acylhomoserine lactone quorum-sensing signals in the culture medium, and (iii) survives mainly by one of these two defense mechanisms, rather than by genetic mutation to phage resistance. Taken together, our results demonstrate thatV. anguillarumemploys quorum-sensing information to choose between two complementary antiphage defense strategies. Further, the prevalence of nonmutational defense mechanisms in strain PF430-3 suggests highly flexible adaptations to KVP40 phage infection pressure, possibly allowing the long-term coexistence of phage and host.IMPORTANCEComprehensive knowledge on bacterial antiphage strategies and their regulation is essential for understanding the role of phages as drivers of bacterial evolution and diversity. In an applied context, development of successful phage-based control of bacterial pathogens also requires detailed understanding of the mechanisms of phage protection in pathogenic bacteria. Here, we demonstrate for the first time the presence of quorum-sensing-regulated phage defense mechanisms in the fish pathogenVibrio anguillarumand provide evidence that quorum-sensing regulation allowsV. anguillarumto alternate between different phage protection mechanisms depending on population cell density. Further, our results demonstrate the prevalence of nonmutational defense mechanisms in the investigatedV. anguillarumstrain, which allow flexible adaptations to a dynamic phage infection pressure.

scholarly journals Disruption of Cell-to-Cell Signaling Does Not Abolish the Antagonism of Phaeobacter gallaeciensis toward the Fish Pathogen Vibrio anguillarum in Algal Systems

2013 ◽  
Vol 79 (17) ◽  
pp. 5414-5417 ◽  
Author(s):  
M. J. Prol García ◽  
P. W. D'Alvise ◽  
L. Gram
Keyword(s):  
Quorum Sensing ◽  
Cell Signaling ◽  
Disease Control ◽  
Vibrio Anguillarum ◽  
Fish Pathogen ◽  
Wild Type ◽  
Content Type ◽  
Phaeobacter Gallaeciensis ◽  
Algal Cultures

ABSTRACTQuorum sensing (QS) regulatesPhaeobacter gallaeciensisantagonism in broth systems; however, we demonstrate here that QS is not important for antagonism in algal cultures. QS mutants reducedVibrio anguillarumto the same extent as the wild type. Consequently, a combination of probioticPhaeobacterand QS inhibitors is a feasible strategy for aquaculture disease control.

scholarly journals Modulation of Pseudomonas aeruginosa Quorum Sensing by Glutathione

2019 ◽  
Vol 201 (9) ◽  
Author(s):  
Hui Zhou ◽  
Meizhen Wang ◽  
Nicole E. Smalley ◽  
Maxim Kostylev ◽  
Amy L. Schaefer ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Transcription Factor ◽  
Transcription Factors ◽  
Quorum Sensing ◽  
Cell Density ◽  
Redox State ◽  
Gene Activation ◽  
Cellular Redox ◽  
Content Type ◽  
Cellular Redox State

ABSTRACT Pseudomonas aeruginosa uses quorum sensing (QS) to regulate the production of a battery of secreted products. At least some of these products are shared among the population and serve as public goods. When P. aeruginosa is grown on casein as the sole carbon and energy source, the QS-induced extracellular protease elastase is required for growth. We isolated a P. aeruginosa variant, which showed increased production of QS-induced factors after repeated transfers in casein broth. This variant, P. aeruginosa QS*, had a mutation in the glutathione synthesis gene gshA. We describe several experiments that show a gshA coding variant and glutathione affect the QS response. The P. aeruginosa QS transcription factor LasR has a redox-sensitive cysteine (C79). We report that GshA variant cells with a LasR C79S substitution show a similar QS response to that of wild-type P. aeruginosa. Surprisingly, it is not LasR but the QS transcription factor RhlR that is more active in bacteria containing the variant gshA. Our results demonstrate that QS integrates information about cell density and the cellular redox state via glutathione levels. IMPORTANCE Pseudomonas aeruginosa and other bacteria coordinate group behaviors using a chemical communication system called quorum sensing (QS). The QS system of P. aeruginosa is complex, with several regulators and signals. We show that decreased levels of glutathione lead to increased gene activation in P. aeruginosa, which did not occur in a strain carrying the redox-insensitive variant of a transcription factor. The ability of P. aeruginosa QS transcription factors to integrate information about cell density and cellular redox state shows these transcription factors can fine-tune levels of the gene products they control in response to at least two types of signals or cues.

scholarly journals Hierarchical Transcriptional Control of the LuxR Quorum-Sensing Regulon of Vibrio harveyi

2020 ◽  
Vol 202 (14) ◽  
Author(s):  
Ryan R. Chaparian ◽  
Alyssa S. Ball ◽  
Julia C. van Kessel
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Quorum Sensing ◽  
Cell Density ◽  
Regulatory Networks ◽  
Vibrio Harveyi ◽  
Sugar Transport ◽  
Content Type ◽  
Second Tier

ABSTRACT In vibrios, quorum sensing controls hundreds of genes that are required for cell density-specific behaviors including bioluminescence, biofilm formation, competence, secretion, and swarming motility. The central transcription factor in the quorum-sensing pathway is LuxR/HapR, which directly regulates ∼100 genes in the >400-gene regulon of Vibrio harveyi. Among these directly controlled genes are 15 transcription factors, which we predicted would comprise the second tier in the hierarchy of the LuxR regulon. We confirmed that LuxR binds to the promoters of these genes in vitro and quantified the extent of LuxR activation or repression of transcript levels. Transcriptome sequencing (RNA-seq) indicates that most of these transcriptional regulators control only a few genes, with the exception of MetJ, which is a global regulator. The genes regulated by these transcription factors are predicted to be involved in methionine and thiamine biosynthesis, membrane stability, RNA processing, c-di-GMP degradation, sugar transport, and other cellular processes. These data support a hierarchical model in which LuxR directly regulates 15 transcription factors that drive the second level of the gene expression cascade to influence cell density-dependent metabolic states and behaviors in V. harveyi. IMPORTANCE Quorum sensing is important for survival of bacteria in nature and influences the actions of bacterial groups. In the relatively few studied examples of quorum-sensing-controlled genes, these genes are associated with competition or cooperation in complex microbial communities and/or virulence in a host. However, quorum sensing in vibrios controls the expression of hundreds of genes, and their functions are mostly unknown or uncharacterized. In this study, we identify the regulators of the second tier of gene expression in the quorum-sensing system of the aquaculture pathogen Vibrio harveyi. Our identification of regulatory networks and metabolic pathways controlled by quorum sensing can be extended and compared to other Vibrio species to understand the physiology, ecology, and pathogenesis of these organisms.

scholarly journals In VivoProgrammed Gene Expression Based on Artificial Quorum Networks

2015 ◽  
Vol 81 (15) ◽  
pp. 4984-4992 ◽  
Author(s):  
Teng Chu ◽  
Yajun Huang ◽  
Mingyu Hou ◽  
Qiyao Wang ◽  
Jingfan Xiao ◽  
...  
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Cell Density ◽  
Protective Antigen ◽  
Expression System ◽  
Edwardsiella Tarda ◽  
Content Type ◽  
Genetic Components ◽  
Wide Range

ABSTRACTThe quorum sensing (QS) system, as a well-functioning population-dependent gene switch, has been widely applied in many gene circuits in synthetic biology. In our work, an efficient cell density-controlled expression system (QS) was established via engineering of theVibrio fischeri luxI-luxRquorum sensing system. In order to achievein vivoprogrammed gene expression, a synthetic binary regulation circuit (araQS) was constructed by assembling multiple genetic components, including the quorum quenching protein AiiA and the arabinose promoter ParaBAD, into the QS system.In vitroexpression assays verified that the araQS system was initiated only in the absence of arabinose in the medium at a high cell density.In vivoexpression assays confirmed that the araQS system presented anin vivo-triggered and cell density-dependent expression pattern. Furthermore, the araQS system was demonstrated to function well in different bacteria, indicating a wide range of bacterial hosts for use. To explore its potential applicationsin vivo, the araQS system was used to control the production of a heterologous protective antigen in an attenuatedEdwardsiella tardastrain, which successfully evoked efficient immune protection in a fish model. This work suggested that the araQS system could program bacterial expressionin vivoand might have potential uses, including, but not limited to, bacterial vector vaccines.

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 Ethanol Stimulates Trehalose Production through a SpoT-DksA-AlgU-Dependent Pathway inPseudomonas aeruginosa

2019 ◽  
Vol 201 (12) ◽  
Author(s):  
Colleen E. Harty ◽  
Dorival Martins ◽  
Georgia Doing ◽  
Dallas L. Mould ◽  
Michelle E. Clay ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Cell Density ◽  
Sigma Factor ◽  
Strong Support ◽  
Transcriptional Response ◽  
Exponential Phase ◽  
Fermentation Products ◽  
Content Type ◽  
In Cells

ABSTRACTPseudomonas aeruginosafrequently resides among ethanol-producing microbes, making its response to the microbially produced concentrations of ethanol relevant to understanding its biology. Our transcriptome analysis found that genes involved in trehalose metabolism were induced by low concentrations of ethanol, and biochemical assays showed that levels of intracellular trehalose increased significantly upon growth with ethanol. The increase in trehalose was dependent on the TreYZ pathway but not other trehalose-metabolic enzymes (TreS or TreA). The sigma factor AlgU (AlgT), a homolog of RpoE in other species, was required for increased expression of thetreZgene and trehalose levels, but induction was not controlled by the well-characterized proteolysis of its anti-sigma factor, MucA. Growth with ethanol led to increased SpoT-dependent (p)ppGpp accumulation, which stimulates AlgU-dependent transcription oftreZand other AlgU-regulated genes through DksA, a (p)ppGpp and RNA polymerase binding protein. Ethanol stimulation of trehalose also required acylhomoserine lactone (AHL)-mediated quorum sensing (QS), as induction was not observed in a ΔlasRΔrhlRstrain. A network analysis using a model, eADAGE, built from publicly availableP. aeruginosatranscriptome data sets (J. Tan, G. Doing, K. A. Lewis, C. E. Price, et al., Cell Syst 5:63–71, 2017, https://doi.org/10.1016/j.cels.2017.06.003) provided strong support for our model in whichtreZand coregulated genes are controlled by both AlgU- and AHL-mediated QS. Consistent with (p)ppGpp- and AHL-mediated quorum-sensing regulation, ethanol, even when added at the time of culture inoculation, stimulatedtreZtranscript levels and trehalose production in cells from post-exponential-phase cultures but not in cells from exponential-phase cultures. These data highlight the integration of growth and cell density cues in theP. aeruginosatranscriptional response to ethanol.IMPORTANCEPseudomonas aeruginosais often found with bacteria and fungi that produce fermentation products, including ethanol. At concentrations similar to those produced by environmental microbes, we found that ethanol stimulated expression of trehalose-biosynthetic genes and cellular levels of trehalose, a disaccharide that protects against environmental stresses. The induction of trehalose by ethanol required the alternative sigma factor AlgU through DksA- and SpoT-dependent (p)ppGpp. Trehalose accumulation also required AHL quorum sensing and occurred only in post-exponential-phase cultures. This work highlights how cells integrate cell density and growth cues in their responses to products made by other microbes and reveals a new role for (p)ppGpp in the regulation of AlgU activity.

scholarly journals Vibriophages Differentially Influence Biofilm Formation by Vibrio anguillarum Strains

2015 ◽  
Vol 81 (13) ◽  
pp. 4489-4497 ◽  
Author(s):  
Demeng Tan ◽  
Amalie Dahl ◽  
Mathias Middelboe
Keyword(s):  
Biofilm Formation ◽  
Vibrio Anguillarum ◽  
Living Cells ◽  
Phage Infection ◽  
Host Cells ◽  
Free Living ◽  
Marine Aquaculture ◽  
Content Type ◽  
Host Interactions ◽  
Biofilm Development

ABSTRACTVibrio anguillarumis an important pathogen in marine aquaculture, responsible for vibriosis. Bacteriophages can potentially be used to control bacterial pathogens; however, successful application of phages requires a detailed understanding of phage-host interactions under both free-living and surface-associated growth conditions. In this study, we exploredin vitrophage-host interactions in two different strains ofV. anguillarum(BA35 and PF430-3) during growth in microcolonies, biofilms, and free-living cells. Two vibriophages, ΦH20 (Siphoviridae) and KVP40 (Myoviridae), had completely different effects on the biofilm development. Addition of phage ΦH20 to strain BA35 showed efficient control of biofilm formation and density of free-living cells. The interactions between BA35 and ΦH20 were thus characterized by a strong phage control of the phage-sensitive population and subsequent selection for phage-resistant mutants. Addition of phage KVP40 to strain PF430-3 resulted in increased biofilm development, especially during the early stage. Subsequent experiments in liquid cultures showed that addition of phage KVP40 stimulated the aggregation of host cells, which protected the cells against phage infection. By the formation of biofilms, strain PF430-3 created spatial refuges that protected the host from phage infection and allowed coexistence between phage-sensitive cells and lytic phage KVP40. Together, the results demonstrate highly variable phage protection mechanisms in two closely relatedV. anguillarumstrains, thus emphasizing the challenges of using phages to control vibriosis in aquaculture and adding to the complex roles of phages as drivers of prokaryotic diversity and population dynamics.

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

2013 ◽  
Vol 81 (8) ◽  
pp. 2888-2898 ◽  
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.

scholarly journals Vibrio anguillarum Is Genetically and Phenotypically Unaffected by Long-Term Continuous Exposure to the Antibacterial Compound Tropodithietic Acid

2016 ◽  
Vol 82 (15) ◽  
pp. 4802-4810 ◽  
Author(s):  
Bastian Barker Rasmussen ◽  
Torben Grotkjær ◽  
Paul W. D'Alvise ◽  
Guangliang Yin ◽  
Faxing Zhang ◽  
...  
Keyword(s):  
Food Production ◽  
Fish Larvae ◽  
Vibrio Anguillarum ◽  
Resistant Bacteria ◽  
Continuous Exposure ◽  
Fish Pathogen ◽  
Content Type ◽  
Tropodithietic Acid ◽  
Antibacterial Compound

ABSTRACTMinimizing the use of antibiotics in the food production chain is essential for limiting the development and spread of antibiotic-resistant bacteria. One alternative intervention strategy is the use of probiotic bacteria, and bacteria of the marineRoseobacterclade are capable of antagonizing fish-pathogenic vibrios in fish larvae and live feed cultures for fish larvae. The antibacterial compound tropodithietic acid (TDA), an antiporter that disrupts the proton motive force, is key in the antibacterial activity of several roseobacters. Introducing probiotics on a larger scale requires understanding of any potential side effects of long-term exposure of the pathogen to the probionts or any compounds they produce. Here we exposed the fish pathogenVibrio anguillarumto TDA for several hundred generations in an adaptive evolution experiment. No tolerance or resistance arose during the 90 days of exposure, and whole-genome sequencing of TDA-exposed lineages and clones revealed few mutational changes, compared to lineages grown without TDA. Amino acid-changing mutations were found in two to six different genes per clone; however, no mutations appeared unique to the TDA-exposed lineages or clones. None of the virulence genes ofV. anguillarumwas affected, and infectivity assays using fish cell lines indicated that the TDA-exposed lineages and clones were less invasive than the wild-type strain. Thus, long-term TDA exposure does not appear to result in TDA resistance and the physiology ofV. anguillarumappears unaffected, supporting the application of TDA-producing roseobacters as probiotics in aquaculture.IMPORTANCEIt is important to limit the use of antibiotics in our food production, to reduce the risk of bacteria developing antibiotic resistance. We showed previously that marine bacteria of theRoseobacterclade can prevent or reduce bacterial diseases in fish larvae, acting as probiotics. Roseobacters produce the antimicrobial compound tropodithietic acid (TDA), and we were concerned regarding whether long-term exposure to this compound could induce resistance or affect the disease-causing ability of the fish pathogen. Therefore, we exposed the fish pathogenVibrio anguillarumto increasing TDA concentrations over 3 months. We did not see the development of any resistance to TDA, and subsequent infection assays revealed that none of the TDA-exposed clones had increased virulence toward fish cells. Hence, this study supports the use of roseobacters as a non-risk-based disease control measure in aquaculture.

scholarly journals Quorum-Sensing Mechanisms Mediated by Farnesol in Ophiostoma piceae: Effect on Secretion of Sterol Esterase

2015 ◽  
Vol 81 (13) ◽  
pp. 4351-4357 ◽  
Author(s):  
Felipe de Salas ◽  
María Jesús Martínez ◽  
Jorge Barriuso
Keyword(s):  
Quorum Sensing ◽  
Cell Density ◽  
Transcriptional Analysis ◽  
Morphological Transition ◽  
Dimorphic Fungus ◽  
Dimorphic Fungi ◽  
Content Type ◽  
Ophiostoma Piceae ◽  
Enhanced Production ◽  
Sterol Esterase

ABSTRACTOphiostoma piceaeCECT 20416 is a dimorphic wood-staining fungus able to produce an extracellular sterol-esterase/lipase (OPE) that is of great biotechnological interest. In this work, we have studied the morphological change of this fungus from yeast to hyphae, which is associated with the cell density-related mechanism known as quorum sensing (QS), and how this affects the secretion of OPE. The data presented here confirm that the moleculeE,E-farnesol accumulates as the cell number is growing within the population. The exogenous addition of this molecule or spent medium to the cultures increased the extracellular activity of OPE 2.5 times. This fact was related not to an increase in microbial biomass or in the expression of the gene coding for OPE but to a marked morphological transition in the cultures. Moreover, the morphological transition also occurred when a high cell density was inoculated into the medium. The results suggest thatE,E-farnesol regulates through QS mechanisms the morphological transition in the dimorphic fungusO. piceaeand that it is associated with a higher extracellular esterase activity. Furthermore, identification and transcriptional analysis of genestup1andcyr1, which are involved in the response, was carried out. Here we report enhanced production of a sterol-esterase/lipase of biotechnological interest by means of QS mechanisms. These results may be useful in increasing the production of secreted enzymes of other dimorphic fungi of biotechnological interest.

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