Pseudomonas aeruginosa reaches collective decisions via transient segregation of quorum sensing activities across cells

Bacteria engage in a cell-to-cell communication process called quorum sensing (QS) to coordinate expression of cooperative exoproducts at the group level. While population-level QS-responses are well studied, we know little about commitments of single cells to QS. Here, we use flow cytometry to track the investment of Pseudomonas aeruginosa individuals into their intertwined Las and Rhl QS-systems. Using fluorescent reporters, we show that QS gene expression (signal synthase, receptor and exoproduct) was heterogenous and followed a gradual instead of a sharp temporal induction pattern. The simultaneous monitoring of two QS genes revealed that cells transiently segregate into low receptor (lasR) expressers that fully commit to QS, and high receptor expressers that delay QS commitment. Our mathematical model shows that such gene expression segregation could mechanistically be spurred by transcription factor limitation. In evolutionary terms, temporal segregation could serve as a QS-brake to allow for a bet-hedging strategy in unpredictable environments.

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The PqsE-RhlR Interaction Regulates RhlR DNA Binding to Control Virulence Factor Production in Pseudomonas aeruginosa

Microbiology Spectrum ◽

10.1128/spectrum.02108-21 ◽

2022 ◽

Author(s):

Kayla A. Simanek ◽

Isabelle R. Taylor ◽

Erica K. Richael ◽

Erica Lasek-Nesselquist ◽

Bonnie L. Bassler ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Dna Binding ◽

Quorum Sensing ◽

Virulence Factor ◽

Cell Communication ◽

Communication Process ◽

Collective Behaviors ◽

Factor Production ◽

A Cell ◽

Virulence Factor Production

Bacteria use a cell-cell communication process called quorum sensing (QS) to orchestrate collective behaviors. QS relies on the group-wide detection of molecules called autoinducers (AI).

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Pseudomonas aeruginosa tolerance to tobramycin, hydrogen peroxide and polymorphonuclear leukocytes is quorum-sensing dependent

Microbiology ◽

10.1099/mic.0.27463-0 ◽

2005 ◽

Vol 151 (2) ◽

pp. 373-383 ◽

Cited By ~ 312

Author(s):

Thomas Bjarnsholt ◽

Peter Østrup Jensen ◽

Mette Burmølle ◽

Morten Hentzer ◽

Janus A. J. Haagensen ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Polymorphonuclear Leukocytes ◽

Present Report ◽

Cell Communication ◽

A Cell ◽

Opportunistic Human Pathogen ◽

Conventional Antibiotics

The opportunistic human pathogen Pseudomonas aeruginosa is the predominant micro-organism of chronic lung infections in cystic fibrosis (CF) patients. P. aeruginosa colonizes the CF lungs by forming biofilm structures in the alveoli. In the biofilm mode of growth the bacteria are highly tolerant to otherwise lethal doses of antibiotics and are protected from bactericidal activity of polymorphonuclear leukocytes (PMNs). P. aeruginosa controls the expression of many of its virulence factors by means of a cell–cell communication system termed quorum sensing (QS). In the present report it is demonstrated that biofilm bacteria in which QS is blocked either by mutation or by administration of QS inhibitory drugs are sensitive to treatment with tobramycin and H2O2, and are readily phagocytosed by PMNs, in contrast to bacteria with functional QS systems. In contrast to the wild-type, QS-deficient biofilms led to an immediate respiratory-burst activation of the PMNs in vitro. In vivo QS-deficient mutants provoked a higher degree of inflammation. It is suggested that quorum signals and QS-inhibitory drugs play direct and opposite roles in this process. Consequently, the faster and highly efficient clearance of QS-deficient bacteria in vivo is probably a two-sided phenomenon: down regulation of virulence and activation of the innate immune system. These data also suggest that a combination of the action of PMNs and QS inhibitors along with conventional antibiotics would eliminate the biofilm-forming bacteria before a chronic infection is established.

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Global H-NS counter-silencing by LuxR activates quorum sensing gene expression

Nucleic Acids Research ◽

10.1093/nar/gkz1089 ◽

2019 ◽

Cited By ~ 6

Author(s):

Ryan R Chaparian ◽

Minh L N Tran ◽

Laura C Miller Conrad ◽

Douglas B Rusch ◽

Julia C van Kessel

Keyword(s):

Gene Expression ◽

Quorum Sensing ◽

Cell Communication ◽

Binding Activity ◽

Primary Role ◽

Dna Binding Activity ◽

Cellular Behaviors ◽

A Cell ◽

Promoter Dna

Abstract Bacteria coordinate cellular behaviors using a cell–cell communication system termed quorum sensing. In Vibrio harveyi, the master quorum sensing transcription factor LuxR directly regulates >100 genes in response to changes in population density. Here, we show that LuxR derepresses quorum sensing loci by competing with H-NS, a global transcriptional repressor that oligomerizes on DNA to form filaments and bridges. We first identified H-NS as a repressor of bioluminescence gene expression, for which LuxR is a required activator. In an hns deletion strain, LuxR is no longer necessary for transcription activation of the bioluminescence genes, suggesting that the primary role of LuxR is to displace H-NS to derepress gene expression. Using RNA-seq and ChIP-seq, we determined that H-NS and LuxR co-regulate and co-occupy 28 promoters driving expression of 63 genes across the genome. ChIP-PCR assays show that as autoinducer concentration increases, LuxR protein accumulates at co-occupied promoters while H-NS protein disperses. LuxR is sufficient to evict H-NS from promoter DNA in vitro, which is dependent on LuxR DNA binding activity. From these findings, we propose a model in which LuxR serves as a counter-silencer at H-NS-repressed quorum sensing loci by disrupting H-NS nucleoprotein complexes that block transcription.

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A structural perspective on the mechanisms of quorum sensing activation in bacteria

Anais da Academia Brasileira de Ciências ◽

10.1590/0001-3765201520140482 ◽

2015 ◽

Vol 87 (4) ◽

pp. 2189-2203 ◽

Cited By ~ 5

Author(s):

CAROLINA LIXA ◽

AMANDA MUJO ◽

CRISTIANE D. ANOBOM ◽

ANDERSON S. PINHEIRO

Keyword(s):

Gene Expression ◽

Quorum Sensing ◽

Rational Design ◽

Three Dimensional ◽

Cell Communication ◽

Dependent Manner ◽

Regulate Gene Expression ◽

Wide Range ◽

A Cell ◽

Regulate Gene

Bacteria are able to synchronize the population behavior in order to regulate gene expression through a cell-to-cell communication mechanism called quorum sensing. This phenomenon involves the production, detection and the response to extracellular signaling molecules named autoinducers, which directly or indirectly regulate gene expression in a cell density-dependent manner. Quorum sensing may control a wide range of biological processes in bacteria, such as bioluminescence, virulence factor production, biofilm formation and antibiotic resistance. The autoinducers are recognized by specific receptors that can either be membrane-bound histidine kinase receptors, which work by activating cognate cytoplasmic response regulators, or cytoplasmic receptors acting as transcription factors. In this review, we focused on the cytosolic quorum sensing regulators whose three-dimensional structures helped elucidate their mechanisms of action. Structural studies of quorum sensing receptors may enable the rational design of inhibitor molecules. Ultimately, this approach may represent an effective alternative to treat infections where classical antimicrobial therapy fails to overcome the microorganism virulence.

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ThePseudomonas aeruginosaOrphan Quorum Sensing Signal Receptor QscR Regulates Global Quorum Sensing Gene Expression by Activating a Single Linked Operon

mBio ◽

10.1128/mbio.01274-18 ◽

2018 ◽

Vol 9 (4) ◽

Cited By ~ 15

Author(s):

Fengming Ding ◽

Ken-Ichi Oinuma ◽

Nicole E. Smalley ◽

Amy L. Schaefer ◽

Omar Hamwy ◽

...

Keyword(s):

Gene Expression ◽

Pseudomonas Aeruginosa ◽

Transcription Factor ◽

Quorum Sensing ◽

Cell Communication ◽

Homoserine Lactone ◽

Acyl Homoserine Lactone ◽

Null Mutant ◽

Content Type ◽

Single Operon

ABSTRACTPseudomonas aeruginosauses two acyl-homoserine lactone signals and two quorum sensing (QS) transcription factors, LasR and RhlR, to activate dozens of genes. LasR responds toN-3-oxo-dodecanoyl-homoserine lactone (3OC12-HSL) and RhlR toN-butanoyl-homoserine lactone (C4-HSL). There is a thirdP. aeruginosaacyl-homoserine-lactone-responsive transcription factor, QscR, which acts to dampen or delay activation of genes by LasR and RhlR by an unknown mechanism. To better understand the role of QscR inP. aeruginosaQS, we performed a chromatin immunoprecipitation analysis, which showed this transcription factor bound the promoter of only a single operon of three genes linked toqscR, PA1895 to PA1897. Other genes that appear to be regulated by QscR in transcriptome studies were not direct targets of QscR. Deletion of PA1897 recapitulates the early QS activation phenotype of a QscR-null mutant, and the phenotype of a QscR-null mutant was complemented by PA1895-1897 but not by PA1897 alone. We conclude that QscR acts to modulate quorum sensing through regulation of a single operon, apparently raising the QS threshold of the population and providing a “brake” on QS autoinduction.IMPORTANCEQuorum sensing, a cell-cell communication system, is broadly distributed among bacteria and is commonly used to regulate the production of shared products. An important consequence of quorum sensing is a delay in production of certain products until the population density is high. The bacteriumPseudomonas aeruginosahas a particularly complicated quorum sensing system involving multiple signals and receptors. One of these receptors, QscR, downregulates gene expression, unlike the other receptors inP. aeruginosa. QscR does so by inducing the expression of a single operon whose function provides an element of resistance to a population reaching a quorum. This finding has importance for design of quorum sensing inhibitory strategies and can also inform design of synthetic biological circuits that use quorum sensing receptors to regulate gene expression.

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Traditional Chinese Medicine Tanreqing Inhibits Quorum Sensing Systems in Pseudomonas aeruginosa

Frontiers in Microbiology ◽

10.3389/fmicb.2020.517462 ◽

2020 ◽

Vol 11 ◽

Author(s):

Weifeng Yang ◽

Qing Wei ◽

Qian Tong ◽

Kaiyu Cui ◽

Gaiying He ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Chinese Medicine ◽

Traditional Chinese Medicine ◽

Quorum Sensing ◽

Virulence Factors ◽

Bacterial Infections ◽

Cell Communication ◽

Opportunistic Pathogen ◽

Communication Process ◽

Phenotypic Analysis

Pseudomonas aeruginosa is an opportunistic pathogen that can infect a wide variety of hosts including humans, plants, and animals. The production of virulence factors is the determinant of the infection paradigm and is under orchestrated regulation via cell-to-cell communication process called quorum sensing (QS). To disable QS circuits and prevent bacterial infections, a large battery of anti-QS agents, particularly from traditional Chinese medicine have been developed. Here, we used P. aeruginosa as a model microorganism to investigate the effect of traditional Chinese medicine Tanreqing (TRQ) formula on bacterial pathogenicity. Phenotypic analysis showed that TRQ treatment could completely inhibit the production of phenazine pyocyanin and moderately inhibit the production of virulence factors such as rhamnolipids, elastase, and alkaline protease. Further transcriptomic analyses revealed that TRQ treatment could significantly attenuate the expression of QS-regulated genes in P. aeruginosa and TRQ-treated P. aeruginosa regulon shared a large overlap with QS regulon. Component contribution to QS inhibition shed light on the indispensable role of all five components in TRQ formula. Further genetic analysis indicated that upstream regulators of QS systems, including two-component systems GacS/GacA and PprA/PprB, were both inhibited by TRQ treatment. Finally, our TRQ formula could efficiently protect Caenorhabditis elegans from killing by P. aeruginosa. Altogether, we have proved TRQ formula as an effective and specific agent to attenuate bacterial virulence and combat bacterial infections.

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Global H-NS counter-silencing by LuxR activates quorum sensing gene expression

10.1101/738146 ◽

2019 ◽

Author(s):

Ryan R. Chaparian ◽

Minh L. N. Tran ◽

Laura C. Miller Conrad ◽

Douglas B. Rusch ◽

Julia C. van Kessel

Keyword(s):

Gene Expression ◽

Quorum Sensing ◽

Cell Communication ◽

Binding Activity ◽

Primary Role ◽

Dna Binding Activity ◽

Cellular Behaviors ◽

A Cell ◽

Promoter Dna

AbstractBacteria coordinate cellular behaviors using a cell-cell communication system termed quorum sensing. In Vibrio harveyi, the master quorum sensing transcriptional factor LuxR directly regulates >100 genes in response to changes in population density. Here, we show that LuxR derepresses quorum sensing loci by competing with H-NS, a global transcriptional repressor that oligomerizes on DNA to form filaments and bridges. We first identified H-NS as a repressor of bioluminescence gene expression, for which LuxR is a required activator. In an hns deletion strain, LuxR is no longer necessary for transcription activation of the bioluminescence genes, suggesting that the primary role of LuxR is to displace H-NS to derepress gene expression. Using RNA-seq and ChIP-seq, we determined that H-NS and LuxR co-regulate and co-occupy 28 promoters driving expression of 63 genes across the genome. ChIP-PCR assays show that as autoinducer concentration increases, LuxR protein accumulates at co-occupied promoters while H-NS protein disperses. LuxR is sufficient to evict H-NS from promoter DNA in vitro, which is dependent on LuxR DNA binding activity. From these findings, we propose a model in which LuxR serves as a counter-silencer at H-NS-repressed quorum sensing loci by disrupting H-NS nucleoprotein complexes that block transcription.

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Faculty Opinions recommendation of A cell-cell communication signal integrates quorum sensing and stress response.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.717995806.793476388 ◽

2013 ◽

Author(s):

Fergal O'Gara

Keyword(s):

Stress Response ◽

Quorum Sensing ◽

Cell Communication ◽

Communication Signal ◽

A Cell ◽

Cell Cell

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Peptide Mix from Olivancillaria hiatula Interferes with Cell-to-Cell Communication in Pseudomonas aeruginosa

BioMed Research International ◽

10.1155/2019/5313918 ◽

2019 ◽

Vol 2019 ◽

pp. 1-12

Author(s):

Edward Ntim Gasu ◽

Hubert Senanu Ahor ◽

Lawrence Sheringham Borquaye

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Biofilm Formation ◽

Antimicrobial Agents ◽

Cell Communication ◽

Microtiter Plate ◽

Antibiofilm Activity ◽

Dependent Manner ◽

Biofilm Inhibition ◽

Swarming Motility

Bacteria in biofilms are encased in an extracellular polymeric matrix that limits exposure of microbial cells to lethal doses of antimicrobial agents, leading to resistance. In Pseudomonas aeruginosa, biofilm formation is regulated by cell-to-cell communication, called quorum sensing. Quorum sensing facilitates a variety of bacterial physiological functions such as swarming motility and protease, pyoverdine, and pyocyanin productions. Peptide mix from the marine mollusc, Olivancillaria hiatula, has been studied for its antibiofilm activity against Pseudomonas aeruginosa. Microscopy and microtiter plate-based assays were used to evaluate biofilm inhibitory activities. Effect of the peptide mix on quorum sensing-mediated processes was also evaluated. Peptide mix proved to be a good antibiofilm agent, requiring less than 39 μg/mL to inhibit 50% biofilm formation. Micrographs obtained confirmed biofilm inhibition at 1/2 MIC whereas 2.5 mg/mL was required to degrade preformed biofilm. There was a marked attenuation in quorum sensing-mediated phenotypes as well. At 1/2 MIC of peptide, the expression of pyocyanin, pyoverdine, and protease was inhibited by 60%, 72%, and 54%, respectively. Additionally, swarming motility was repressed by peptide in a dose-dependent manner. These results suggest that the peptide mix from Olivancillaria hiatula probably inhibits biofilm formation by interfering with cell-to-cell communication in Pseudomonas aeruginosa.

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