Protist predation can favour cooperation within bacterial species

Here, we studied how protist predation affects cooperation in the opportunistic pathogen bacterium Pseudomonas aeruginosa , which uses quorum sensing (QS) cell-to-cell signalling to regulate the production of public goods. By competing wild-type bacteria with QS mutants (cheats), we show that a functioning QS system confers an elevated resistance to predation. Surprisingly, cheats were unable to exploit this resistance in the presence of cooperators, which suggests that resistance does not appear to result from activation of QS-regulated public goods. Instead, elevated resistance of wild-type bacteria was related to the ability to form more predation-resistant biofilms. This could be explained by the expression of QS-regulated resistance traits in densely populated biofilms and floating cell aggregations, or alternatively, by a pleiotropic cost of cheating where less resistant cheats are selectively removed from biofilms. These results show that trophic interactions among species can maintain cooperation within species, and have further implications for P. aeruginosa virulence in environmental reservoirs by potentially enriching the cooperative and highly infective strains with functional QS system.

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Discovery of an inhibitor of the production of the Pseudomonas aeruginosa virulence factor pyocyanin in wild-type cells

Beilstein Journal of Organic Chemistry ◽

10.3762/bjoc.12.137 ◽

2016 ◽

Vol 12 ◽

pp. 1428-1433 ◽

Cited By ~ 8

Author(s):

Bernardas Morkunas ◽

Balint Gal ◽

Warren R J D Galloway ◽

James T Hodgkinson ◽

Brett M Ibbeson ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Cell Signalling ◽

Opportunistic Pathogen ◽

Wild Type ◽

Wide Range ◽

Potential Applications ◽

Therapeutic Context ◽

Pyocyanin Production

Pyocyanin is a small molecule produced by Pseudomonas aeruginosa that plays a crucial role in the pathogenesis of infections by this notorious opportunistic pathogen. The inhibition of pyocyanin production has been identified as an attractive antivirulence strategy for the treatment of P. aeruginosa infections. Herein, we report the discovery of an inhibitor of pyocyanin production in cultures of wild-type P. aeruginosa which is based around a 4-alkylquinolin-2(1H)-one scaffold. To the best of our knowledge, this is the first reported example of pyocyanin inhibition by a compound based around this molecular framework. The compound may therefore be representative of a new structural sub-class of pyocyanin inhibitors, which could potentially be exploited in in a therapeutic context for the development of critically needed new antipseudomonal agents. In this context, the use of wild-type cells in this study is notable, since the data obtained are of direct relevance to native situations. The compound could also be of value in better elucidating the role of pyocyanin in P. aeruginosa infections. Evidence suggests that the active compound reduces the level of pyocyanin production by inhibiting the cell–cell signalling mechanism known as quorum sensing. This could have interesting implications; quorum sensing regulates a range of additional elements associated with the pathogenicity of P. aeruginosa and there is a wide range of other potential applications where the inhibition of quorum sensing is desirable.

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The fitness ofPseudomonas aeruginosaquorum sensing signal cheats is influenced by the diffusivity of the environment

10.1101/082230 ◽

2016 ◽

Cited By ~ 1

Author(s):

Anne Mund ◽

Stephen P. Diggle ◽

Freya Harrison

Keyword(s):

Quorum Sensing ◽

Public Goods ◽

Social Dynamics ◽

Population Level ◽

Opportunistic Pathogen ◽

Signal Molecules ◽

Wild Type ◽

Signaling Systems ◽

Environmental Structure ◽

Bacterial Quorum

ABSTRACTExperiments examining the social dynamics of bacterial quorum sensing (QS) have focused on mutants which do not respond to signals, and the role of QS-regulated exoproducts as public goods. The potential for QS signal molecules to themselves be social public goods has received much less attention. Here, we analyse how signal-deficient (lasI−) mutants of the opportunistic pathogenPseudomonas aeruginosainteract with wild-type cells in an environment where QS is required for growth. We show that when growth requires a ‘private’ intracellular metabolic mechanism activated by the presence of QS signal,lasI−mutants act as social cheats and outcompete signal-producing wild-type bacteria in mixed cultures, because they can use the signals produced by wild type cells. However, reducing the ability of signal molecules to diffuse through the growth medium, results in signal molecules becoming less accessible to mutants, leading to reduced cheating. Our results indicate that QS signal molecules can be considered as social public goods in a way that has been previously described for other exoproducts, but that spatial structuring of populations reduces exploitation by non-cooperative signal cheats.ImportanceBacteria communicate via signaling molecules to regulate the expression of a whole range of genes. This process, termed quorum sensing (QS), moderates bacterial metabolism in many environmental conditions, from soil and water (where QS-regulated genes influence nutrient cycling) to animal hosts (where QS-regulated genes determine pathogen virulence). Understanding the ecology of QS could therefore yield vital clues as to how we might modify bacterial behaviour for environmental or clinical gains. Here, we demonstrate that QS signals act as shareable public goods. This means that their evolution, and therefore population-level responses to interference with QS, will be constrained by population structure. Further, we show that environmental structure (constraints on signal diffusion) alters the accessibility of QS signals and demonstrates that we need to consider population and environmental structure to help us further our understanding of QS signaling systems.

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Pseudomonas aeruginosa Las quorum sensing autoinducer suppresses growth and biofilm production in Legionella species

Microbiology ◽

10.1099/mic.0.026641-0 ◽

2009 ◽

Vol 155 (6) ◽

pp. 1934-1939 ◽

Cited By ~ 32

Author(s):

Soichiro Kimura ◽

Kazuhiro Tateda ◽

Yoshikazu Ishii ◽

Manabu Horikawa ◽

Shinichi Miyairi ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Legionella Pneumophila ◽

Bacterial Species ◽

Cell Signalling ◽

Homoserine Lactone ◽

Alcaligenes Faecalis ◽

Suppressive Effect ◽

Dependent Manner ◽

A Cell

Bacteria commonly communicate with each other by a cell-to-cell signalling mechanism known as quorum sensing (QS). Recent studies have shown that the Las QS autoinducer N-(3-oxododecanoyl)-l-homoserine lactone (3-oxo-C12-HSL) of Pseudomonas aeruginosa performs a variety of functions not only in intraspecies communication, but also in interspecies and interkingdom interactions. In this study, we report the effects of Pseudomonas 3-oxo-C12-HSL on the growth and suppression of virulence factors in other bacterial species that frequently co-exist with Ps. aeruginosa in nature. It was found that 3-oxo-C12-HSL, but not its analogues, suppressed the growth of Legionella pneumophila in a dose-dependent manner. However, 3-oxo-C12-HSL did not exhibit a growth-suppressive effect on Serratia marcescens, Proteus mirabilis, Escherichia coli, Alcaligenes faecalis and Stenotrophomonas maltophilia. A concentration of 50 μM 3-oxo-C12-HSL completely inhibited the growth of L. pneumophila. Additionally, a significant suppression of biofilm formation was demonstrated in L. pneumophila exposed to 3-oxo-C12-HSL. Our results suggest that the Pseudomonas QS autoinducer 3-oxo-C12-HSL exerts both bacteriostatic and virulence factor-suppressive activities on L. pneumophila alone.

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Quorum Sensing Protects Pseudomonas aeruginosa against Cheating by Other Species in a Laboratory Coculture Model

Journal of Bacteriology ◽

10.1128/jb.00482-15 ◽

2015 ◽

Vol 197 (19) ◽

pp. 3154-3159 ◽

Cited By ~ 28

Author(s):

Nicole E. Smalley ◽

Dingding An ◽

Matthew R. Parsek ◽

Josephine R. Chandler ◽

Ajai A. Dandekar

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Public Goods ◽

Public Good ◽

Hydrogen Cyanide ◽

Cooperative Behavior ◽

Bacterial Species ◽

Cell Communication ◽

Content Type ◽

Burkholderia Multivorans

ABSTRACTMany species of bacteria use a cell-cell communication system called quorum sensing (QS) to coordinate group activities. QS systems frequently regulate the production of exoproducts. Some of these products, such as proteases, are “public goods” that are shared among the population and vulnerable to cheating by nonproducing members of the population. Because the QS system of the opportunistic pathogenPseudomonas aeruginosaregulates several public goods, it can serve as a model for studying cooperation. Bacteria also commonly regulate antimicrobial production through QS. In this study, we focused on the hypothesis that QS-regulated antimicrobials may be important forP. aeruginosato protect against cheating by another bacterial species,Burkholderia multivorans.We assessed laboratory cocultures ofP. aeruginosaandB. multivoransand investigated the importance of threeP. aeruginosaQS-regulated antimicrobials, hydrogen cyanide, rhamnolipids, and phenazines, for competition. We found thatP. aeruginosadominates cocultures withB. multivoransand that the three antimicrobials together promoteP. aeruginosacompetitiveness, with hydrogen cyanide contributing the greatest effect. We show that these QS-regulated antimicrobials are also critical forP. aeruginosato preventB. multivoransfrom cheating under nutrient conditions where both species require aP. aeruginosaquorum-regulated protease for growth. Together our results highlight the importance of antimicrobials in protecting cooperating populations from exploitation by other species that can act as cheaters.IMPORTANCECooperative behaviors are threatened by social cheating, wherein individuals do not produce but nonetheless benefit from shared public goods. Bacteria have been shown to use several genetic mechanisms to restrain the emergence of cheaters from within the population, but public goods might also be used by other bacterial species in the vicinity. We demonstrate that a public good produced byPseudomonas aeruginosacan be used by another species,Burkholderia multivorans, to obtain carbon and energy. We also show thatP. aeruginosaantimicrobials that are coregulated with the public good prevent invasion by the cheating species. Our results demonstrate that cross-species cheating can occur and that coregulation of public goods with antimicrobials may stabilize cooperative behavior in mixed microbial communities.

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Pseudomonas aeruginosa Increases Formation of Multidrug-Tolerant Persister Cells in Response to Quorum-Sensing Signaling Molecules

Journal of Bacteriology ◽

10.1128/jb.01231-09 ◽

2010 ◽

Vol 192 (7) ◽

pp. 1946-1955 ◽

Cited By ~ 140

Author(s):

Nina Möker ◽

Charles R. Dean ◽

Jianshi Tao

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Bacterial Species ◽

Opportunistic Pathogen ◽

Homoserine Lactone ◽

Signaling Molecules ◽

Persister Cells ◽

E Coli ◽

Underlying Mechanisms ◽

Lethal Doses

ABSTRACT Bacterial persister cells constitute a small portion of a culture which is tolerant to killing by lethal doses of bactericidal antibiotics. These phenotypic variants are formed in numerous bacterial species, including those with clinical relevance like the opportunistic pathogen Pseudomonas aeruginosa. Although persisters are believed to contribute to difficulties in the treatment of many infectious diseases, the underlying mechanisms affecting persister formation are not well understood. Here we show that even though P. aeruginosa cultures have a significantly smaller fraction of multidrug-tolerant persister cells than cultures of Escherichia coli or Staphylococcus aureus, they can increase persister numbers in response to quorum-sensing-related signaling molecules. The phenazine pyocyanin (and the closely related molecule paraquat) and the acyl-homoserine lactone 3-OC12-HSL significantly increased the persister numbers in logarithmic P. aeruginosa PAO1 or PA14 cultures but not in E. coli or S. aureus cultures.

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Pseudomonas aeruginosa extracellular products inhibit staphylococcal growth, and disrupt established biofilms produced by Staphylococcus epidermidis

Microbiology ◽

10.1099/mic.0.028001-0 ◽

2009 ◽

Vol 155 (7) ◽

pp. 2148-2156 ◽

Cited By ~ 81

Author(s):

Zhiqiang Qin ◽

Liang Yang ◽

Di Qu ◽

Soeren Molin ◽

Tim Tolker-Nielsen

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Staphylococcus Epidermidis ◽

Bacterial Species ◽

Opportunistic Pathogen ◽

Nosocomial Pathogen ◽

Microbial Competition ◽

Polysaccharide Biosynthesis ◽

Extracellular Products ◽

Novel Strategy

Multiple bacterial species often coexist as communities, and compete for environmental resources. Here, we describe how an opportunistic pathogen, Pseudomonas aeruginosa, uses extracellular products to interact with the nosocomial pathogen Staphylococcus epidermidis. S. epidermidis biofilms and planktonic cultures were challenged with P. aeruginosa supernatant cultures overnight. Results indicated that quorum-sensing-controlled factors from P. aeruginosa supernatant inhibited S. epidermidis growth in planktonic cultures. We also found that P. aeruginosa extracellular products, mainly polysaccharides, disrupted established S. epidermidis biofilms. Cellulase-treated P. aeruginosa supernatant, and supernatant from pelA, pslF and pelApslBCD mutants, which are deficient in polysaccharide biosynthesis, diminished the disruption of S. epidermidis biofilms. In contrast, S. epidermidis supernatant in overnight cultures had no effect on established P. aeruginosa biofilms and planktonic growth. These findings reveal that P. aeruginosa extracellular products are important microbial competition factors that overcome competition with S. epidermidis, and the results may provide clues for the development of a novel strategy for controlling S. epidermidis biofilms.

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Intraspecies Signaling between Common Variants of Pseudomonas aeruginosa Increases Production of Quorum-Sensing-Controlled Virulence Factors

mBio ◽

10.1128/mbio.01865-20 ◽

2020 ◽

Vol 11 (4) ◽

Cited By ~ 2

Author(s):

Dallas L. Mould ◽

Nico J. Botelho ◽

Deborah A. Hogan

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Opportunistic Pathogen ◽

Loss Of Function ◽

Wild Type ◽

Chronic Infections ◽

Content Type ◽

Complex Interactions ◽

Natural Settings ◽

Citrate Release

ABSTRACT The opportunistic pathogen Pseudomonas aeruginosa damages hosts through the production of diverse secreted products, many of which are regulated by quorum sensing (QS). The lasR gene, which encodes a central QS regulator, is frequently mutated in clinical isolates from chronic infections, and loss of LasR function (LasR−) generally impairs the activity of downstream QS regulators RhlR and PqsR. We found that in cocultures containing LasR+ and LasR− strains, LasR− strains hyperproduce the RhlR/RhlI-regulated antagonistic factors pyocyanin and rhamnolipids in diverse models and media and in different strain backgrounds. Diffusible QS autoinducers produced by the wild type were not required for this effect. Using transcriptomics, genetics, and biochemical approaches, we uncovered a reciprocal interaction between wild-type and lasR mutant pairs wherein the iron-scavenging siderophore pyochelin produced by the lasR mutant induced citrate release and cross-feeding from the wild type. Citrate, a metabolite often secreted in low iron environments, stimulated RhlR signaling and RhlI levels in LasR−but not in LasR+ strains. These studies reveal the potential for complex interactions between recently diverged, genetically distinct isolates within populations from single chronic infections. IMPORTANCE Coculture interactions between lasR loss-of-function and LasR+ Pseudomonas aeruginosa strains may explain the worse outcomes associated with the presence of LasR− strains. More broadly, this report illustrates how interactions within a genotypically diverse population, similar to those that frequently develop in natural settings, can promote unpredictably high virulence factor production.

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Intra-species signaling between Pseudomonas aeruginosa genotypes increases production of quorum sensing controlled virulence factors

10.1101/2020.04.29.068346 ◽

2020 ◽

Author(s):

Dallas L. Mould ◽

Nico J. Botelho ◽

Deborah A. Hogan

Keyword(s):

Pseudomonas Aeruginosa ◽

Transcription Factor ◽

Quorum Sensing ◽

Opportunistic Pathogen ◽

Diverse Population ◽

Loss Of Function ◽

Wild Type ◽

Natural Settings ◽

Citrate Release ◽

Virulence Factor Production

AbstractThe opportunistic pathogen Pseudomonas aeruginosa damages hosts through the production of diverse secreted products, many of which are regulated by quorum sensing. The lasR gene, which encodes a central quorum-sensing regulator, is frequently mutated, and loss of LasR function impairs the activity of downstream regulators RhlR and PqsR. We found that in diverse models, the presence of P. aeruginosa wild type causes LasR loss-of-function strains to hyperproduce RhlR/I-regulated antagonistic factors, and autoinducer production by the wild type is not required for this effect. We uncovered a reciprocal interaction between isogenic wild type and lasR mutant pairs wherein the iron-scavenging siderophore pyochelin, specifically produced by the lasR mutant, induces citrate release and cross-feeding from wild type. Citrate stimulates RhlR signaling and RhlI levels in LasR-but not in LasR+ strains, and the interactions occur in diverse media. Co-culture interactions between strains that differ by the function of a single transcription factor may explain worse outcomes associated with mixtures of LasR+ and LasR loss-of-function strains. More broadly, this report illustrates how interactions within a genotypically diverse population, similar to those that frequently develop in natural settings, can promote net virulence factor production.

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Environmental modification via a quorum sensing molecule influences the social landscape of siderophore production

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2017.0200 ◽

2017 ◽

Vol 284 (1852) ◽

pp. 20170200 ◽

Cited By ~ 22

Author(s):

Roman Popat ◽

Freya Harrison ◽

Ana C. da Silva ◽

Scott A. S. Easton ◽

Luke McNally ◽

...

Keyword(s):

Quorum Sensing ◽

Public Goods ◽

Bacterial Species ◽

Relative Fitness ◽

Iron Starvation ◽

Signal Molecule ◽

Signalling Molecules ◽

Signalling Molecule ◽

The Impact ◽

Social Trait

Bacteria produce a wide variety of exoproducts that favourably modify their environment and increase their fitness. These are often termed ‘public goods’ because they are costly for individuals to produce and can be exploited by non-producers (cheats). The outcome of conflict over public goods is dependent upon the prevailing environment and the phenotype of the individuals in competition. Many bacterial species use quorum sensing (QS) signalling molecules to regulate the production of public goods. QS, therefore, determines the cooperative phenotype of individuals, and influences conflict over public goods. In addition to their regulatory functions, many QS molecules have additional properties that directly modify the prevailing environment. This leads to the possibility that QS molecules could influence conflict over public goods indirectly through non-signalling effects, and the impact of this on social competition has not previously been explored. The Pseudomonas aeruginosa QS signal molecule PQS is a powerful chelator of iron which can cause an iron starvation response. Here, we show that PQS stimulates a concentration-dependent increase in the cooperative production of iron scavenging siderophores, resulting in an increase in the relative fitness of non-producing siderophore cheats. This is likely due to an increased cost of siderophore output by producing cells and a concurrent increase in the shared benefits, which accrue to both producers and cheats. Although PQS can be a beneficial signalling molecule for P. aeruginosa , our data suggest that it can also render a siderophore-producing population vulnerable to competition from cheating strains. More generally, our results indicate that the production of one social trait can indirectly affect the costs and benefits of another social trait.

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Pseudomonas aeruginosa las and rhl quorum-sensing systems are important for infection and inflammation in a rat prostatitis model

Microbiology ◽

10.1099/mic.0.028464-0 ◽

2009 ◽

Vol 155 (8) ◽

pp. 2612-2619 ◽

Cited By ~ 21

Author(s):

Lisa K. Nelson ◽

Genevieve H. D'Amours ◽

Kimberley M. Sproule-Willoughby ◽

Douglas W. Morck ◽

Howard Ceri

Keyword(s):

Pseudomonas Aeruginosa ◽

Quorum Sensing ◽

Tissue Damage ◽

Inflammatory Markers ◽

Bacterial Colonization ◽

Opportunistic Pathogen ◽

Infection Model ◽

Chronic Infections ◽

Strain Pao1 ◽

Rat Prostate

Pseudomonas aeruginosa frequently acts as an opportunistic pathogen of mucosal surfaces; yet, despite causing aggressive prostatitis in some men, its role as a pathogen in the prostate has not been investigated. Consequently, we developed a Ps. aeruginosa infection model in the rat prostate by instilling wild-type (WT) Ps. aeruginosa strain PAO1 into the rat prostate. It was found that Ps. aeruginosa produced acute and chronic infections in this mucosal tissue as determined by bacterial colonization, gross morphology, tissue damage and inflammatory markers. WT strain PAO1 and its isogenic mutant PAO-JP2, in which both the lasI and rhlI quorum-sensing signal systems have been silenced, were compared during both acute and chronic prostate infections. In acute infections, bacterial numbers and inflammatory markers were comparable between WT PA01 and PAO-JP2; however, considerably less tissue damage occurred in infections with PAO-JP2. Chronic infections with PAO-JP2 resulted in reduced bacterial colonization, tissue damage and inflammation as compared to WT PAO1 infections. Therefore, the quorum-sensing lasI and rhlI genes in Ps. aeruginosa affect acute prostate infections, but play a considerably more important role in maintaining chronic infections. We have thus developed a highly reproducible model for the study of Ps. aeruginosa virulence in the prostate.

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