1
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Montelongo-Martínez LF, Díaz-Guerrero M, Flores-Vega VR, Soto-Aceves MP, Rosales-Reyes R, Quiroz-Morales SE, González-Pedrajo B, Soberón-Chávez G, Cocotl-Yañez M. The quorum sensing regulator RhlR positively controls the expression of the type III secretion system in Pseudomonas aeruginosa PAO1. PLoS One 2024; 19:e0307174. [PMID: 39146292 PMCID: PMC11326643 DOI: 10.1371/journal.pone.0307174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Accepted: 07/01/2024] [Indexed: 08/17/2024] Open
Abstract
Pseudomonas aeruginosa is an opportunist bacterium that causes acute and chronic infections. During acute infections, the type III secretion system (T3SS) plays a pivotal role in allowing the bacteria to translocate effectors such as ExoS, ExoT, and ExoY into host cells for colonization. Previous research on the involvement of quorum sensing systems Las and Rhl in controlling the T3SS gene expression produced ambiguous results. In this study, we determined the role of the Las and Rhl systems and the PqsE protein on T3SS expression. Our results show that in the wild-type PAO1 strain, the deletion of lasR or pqsE do not affect the secretion of ExoS. However, rhlI inactivation increases the expression of T3SS genes. In contrast to the rhlI deletion, rhlR inactivation decreases both T3SS genes expression and ExoS secreted protein levels, and this phenotype is restored when this mutant is complemented with the exsA gene, which codes for the master regulator of the T3SS. Additionally, cytotoxicity is affected in the rhlR mutant strain compared with its PAO1 parental strain. Overall, our results indicate that neither the Las system nor PqsE are involved in regulating the T3SS. Moreover, the Rhl system components have opposite effects, RhlI participates in negatively controlling the T3SS expression, while RhlR does it in a positive way, and this regulation is independent of C4 or PqsE. Finally, we show that rhlR, rhlI, or pqsE inactivation abolished pyocyanin production in T3SS-induction conditions. The ability of RhlR to act as a positive T3SS regulator in the absence of its cognate autoinducer and PqsE shows that it is a versatile regulator that controls different virulence traits allowing P. aeruginosa to compete for a niche.
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Affiliation(s)
- Luis Fernando Montelongo-Martínez
- Facultad de Medicina, Departamento de Microbiología y Parasitología, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Miguel Díaz-Guerrero
- Facultad de Medicina, Departamento de Microbiología y Parasitología, Universidad Nacional Autónoma de México, Ciudad de México, México
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, México
| | - Verónica Roxana Flores-Vega
- Departamento de Biomedicina Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Ciudad de México, México
| | - Martín Paolo Soto-Aceves
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Roberto Rosales-Reyes
- Facultad de Medicina, Unidad de Medicina Experimental, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Sara Elizabeth Quiroz-Morales
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Bertha González-Pedrajo
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, México
| | - Gloria Soberón-Chávez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Miguel Cocotl-Yañez
- Facultad de Medicina, Departamento de Microbiología y Parasitología, Universidad Nacional Autónoma de México, Ciudad de México, México
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2
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Soto-Aceves MP, Smalley NE, Schaefer AL, Greenberg EP. The Relationship of pqs Gene Expression to Acylhomoserine Lactone Signaling in Pseudomonas aeruginosa. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.22.586172. [PMID: 38562759 PMCID: PMC10983942 DOI: 10.1101/2024.03.22.586172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
The opportunistic pathogen Pseudomonas aeruginosa has complex quorum sensing (QS) circuitry, which involves two acylhomoserine lactone (AHL) systems, the LasI AHL synthase and LasR AHL-dependent transcriptional activator system and the RhlI AHL synthase-RhlR AHL-responsive transcriptional activator. There is also a quinoline signaling system (the Pseudomonas quinolone signal, PQS, system). Although there is a core set of genes regulated by the AHL circuits, there is substantial strain-to-strain variation in the non-core QS regulated genes. Reductive evolution of the QS regulon, and variation in specific genes activated by QS, occurs in laboratory evolution experiments with the model strain PAO1. We used a transcriptomics approach to test the hypothesis that reductive evolution in the PAO1 QS regulon can in large part be explained by a simple null mutation in pqsR , the gene encoding the transcriptional activator of the pqs operon. We found that PqsR had very little influence on the AHL QS regulon. This was a surprising finding because the last gene in the PqsR-dependent pqs operon, pqsE , codes for a protein, which physically interacts with RhlR and this interaction is required for RhlR-dependent activation of some genes. We used comparative transcriptomics to examine the influence of a pqsE mutation on the QS regulon and identified only three transcripts, which were strictly dependent on PqsE. By using reporter constructs we showed that the PqsE influence on other genes was dependent on experimental conditions and we have gained some insight about those conditions. This work adds to our understanding of the plasticity of the P. aeruginosa QS regulon and to the role PqsE plays in RhlR-dependent gene activation.
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Zhou L, Höfte M, Hennessy RC. Does regulation hold the key to optimizing lipopeptide production in Pseudomonas for biotechnology? Front Bioeng Biotechnol 2024; 12:1363183. [PMID: 38476965 PMCID: PMC10928948 DOI: 10.3389/fbioe.2024.1363183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Accepted: 02/12/2024] [Indexed: 03/14/2024] Open
Abstract
Lipopeptides (LPs) produced by Pseudomonas spp. are specialized metabolites with diverse structures and functions, including powerful biosurfactant and antimicrobial properties. Despite their enormous potential in environmental and industrial biotechnology, low yield and high production cost limit their practical use. While genome mining and functional genomics have identified a multitude of LP biosynthetic gene clusters, the regulatory mechanisms underlying their biosynthesis remain poorly understood. We propose that regulation holds the key to unlocking LP production in Pseudomonas for biotechnology. In this review, we summarize the structure and function of Pseudomonas-derived LPs and describe the molecular basis for their biosynthesis and regulation. We examine the global and specific regulator-driven mechanisms controlling LP synthesis including the influence of environmental signals. Understanding LP regulation is key to modulating production of these valuable compounds, both quantitatively and qualitatively, for industrial and environmental biotechnology.
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Affiliation(s)
- Lu Zhou
- Laboratory of Phytopathology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Monica Höfte
- Laboratory of Phytopathology, Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Rosanna C. Hennessy
- Department of Plant and Environmental Sciences, University of Copenhagen, Copenhagen, Denmark
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4
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Muriel-Millán LF, Montelongo-Martínez LF, González-Valdez A, Bedoya-Pérez LP, Cocotl-Yañez M, Soberón-Chávez G. The alternative sigma factor RpoS regulates Pseudomonas aeruginosa quorum sensing response by repressing the pqsABCDE operon and activating vfr. Mol Microbiol 2024; 121:291-303. [PMID: 38169053 DOI: 10.1111/mmi.15224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 12/02/2023] [Accepted: 12/22/2023] [Indexed: 01/05/2024]
Abstract
Pseudomonas aeruginosa is an important opportunistic pathogen. Several of its virulence-related processes, including the synthesis of pyocyanin (PYO) and biofilm formation, are controlled by quorum sensing (QS). It has been shown that the alternative sigma factor RpoS regulates QS through the reduction of lasR and rhlR transcription (encoding QS regulators). However, paradoxically, the absence of RpoS increases PYO production and biofilm development (that are RhlR dependent) by unknown mechanisms. Here, we show that RpoS represses pqsE transcription, which impacts the stability and activity of RhlR. In the absence of RpoS, rhlR transcript levels are reduced but not the RhlR protein concentration, presumably by its stabilization by PqsE, whose expression is increased. We also report that PYO synthesis and the expression of pqsE and phzA1B1C1D1E1F1G1 operon exhibit the same pattern at different RpoS concentrations, suggesting that the RpoS-dependent PYO production is due to its ability to modify PqsE concentration, which in turn modulates the activation of the phzA1 promoter by RhlR. Finally, we demonstrate that RpoS favors the expression of Vfr, which activates the transcription of lasR and rhlR. Our study contributes to the understanding of how RpoS modulates the QS response in P. aeruginosa, exerting both negative and positive regulation.
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Affiliation(s)
- Luis Felipe Muriel-Millán
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, Mexico
| | - Luis Fernando Montelongo-Martínez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, Mexico
| | - Abigail González-Valdez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, Mexico
| | - Leidy Patricia Bedoya-Pérez
- Programa de Biología Sintética, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
| | - Miguel Cocotl-Yañez
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, Mexico
| | - Gloria Soberón-Chávez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, Mexico
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5
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Miranda SW, Greenberg EP. A balancing act: investigations on the impact of altered signal sensitivity in bacterial quorum sensing. J Bacteriol 2023; 205:e0024923. [PMID: 38009926 PMCID: PMC10729764 DOI: 10.1128/jb.00249-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 11/03/2023] [Indexed: 11/29/2023] Open
Abstract
IMPORTANCE Quorum sensing (QS) is a widespread form of cell-cell signaling that regulates group behaviors important for competition and cooperation within bacterial communities. The QS systems from different bacterial species have diverse properties, but the functional consequences of this diversity are largely unknown. Taking advantage of hyper- and hypo-sensitive QS receptor variants in the opportunistic pathogen Pseudomonas aeruginosa, we examine the costs and benefits of altered signal sensitivity. We find that the sensitivity of a model QS receptor, LasR, impacts the timing and level of quorum gene expression, and fitness during intra- and interspecies competition. These findings suggest competition with kin and with other bacterial species work together to tune signal sensitivity.
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Affiliation(s)
| | - E. Peter Greenberg
- Department of Microbiology, University of Washington, Seattle, Washington, USA
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Nazeer RR, Wang M, Welch M. More than just a gel: the extracellular matrixome of Pseudomonas aeruginosa. Front Mol Biosci 2023; 10:1307857. [PMID: 38028553 PMCID: PMC10679415 DOI: 10.3389/fmolb.2023.1307857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 10/31/2023] [Indexed: 12/01/2023] Open
Abstract
Armed with an arsenal of protein secretion systems, antibiotic efflux pumps, and the occasional proclivity for explosive self-destruction, Pseudomonas aeruginosa has become a model for the study of bacterial pathogenesis and biofilm formation. There is accruing evidence to suggest that the biofilm matrix-the bioglue that holds the structure together-acts not only in a structural capacity, but is also a molecular "net" whose function is to capture and retain certain secreted products (including proteins and small molecules). In this perspective, we argue that the biofilm matrixome is a distinct extracellular compartment, and one that is differentiated from the bulk secretome. Some of the points we raise are deliberately speculative, but are becoming increasingly accessible to experimental investigation.
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Affiliation(s)
| | | | - Martin Welch
- Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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7
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de Oliveira Pereira T, Groleau MC, Déziel E. Surface growth of Pseudomonas aeruginosa reveals a regulatory effect of 3-oxo-C 12-homoserine lactone in the absence of its cognate receptor, LasR. mBio 2023; 14:e0092223. [PMID: 37732738 PMCID: PMC10653899 DOI: 10.1128/mbio.00922-23] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 07/26/2023] [Indexed: 09/22/2023] Open
Abstract
IMPORTANCE The bacterium Pseudomonas aeruginosa colonizes and thrives in many environments, in which it is typically found in surface-associated polymicrobial communities known as biofilms. Adaptation to this social behavior is aided by quorum sensing (QS), an intercellular communication system pivotal in the expression of social traits. Regardless of its importance in QS regulation, the loss of function of the master regulator LasR is now considered a conserved adaptation of P. aeruginosa, irrespective of the origin of the strains. By investigating the QS circuitry in surface-grown cells, we found an accumulation of QS signal 3-oxo-C12-HSL in the absence of its cognate receptor and activator, LasR. The current understanding of the QS circuit, mostly based on planktonic growing cells, is challenged by investigating the QS circuitry of surface-grown cells. This provides a new perspective on the beneficial aspects that underline the frequency of LasR-deficient isolates.
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Affiliation(s)
- Thays de Oliveira Pereira
- Centre Armand-Frappier Santé Biotechnologie, Institut National de la Recherche Scientifique (INRS), Laval, Québec, Canada
| | - Marie-Christine Groleau
- Centre Armand-Frappier Santé Biotechnologie, Institut National de la Recherche Scientifique (INRS), Laval, Québec, Canada
| | - Eric Déziel
- Centre Armand-Frappier Santé Biotechnologie, Institut National de la Recherche Scientifique (INRS), Laval, Québec, Canada
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8
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Kesthely CA, Rogers RR, El Hafi B, Jean-Pierre F, O’Toole GA. Transcriptional profiling and genetic analysis of a cystic fibrosis airway-relevant model shows asymmetric responses to growth in a polymicrobial community. Microbiol Spectr 2023; 11:e0220123. [PMID: 37772884 PMCID: PMC10580927 DOI: 10.1128/spectrum.02201-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 08/17/2023] [Indexed: 09/30/2023] Open
Abstract
Bacterial infections in the lungs of persons with cystic fibrosis are typically composed of multispecies biofilm-like communities, which modulate clinically relevant phenotypes that cannot be explained in the context of a single species culture. Most analyses to date provide a picture of the transcriptional responses of individual pathogens; however, there is relatively little data describing the transcriptional landscape of clinically relevant multispecies communities. Harnessing a previously described cystic fibrosis-relevant, polymicrobial community model consisting of Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus sanguinis, and Prevotella melaninogenica, we performed an RNA-Seq analysis on the biofilm population to elucidate the transcriptional profiles of the community grown in artificial sputum medium (ASM) as compared to growth in monoculture, without mucin, and in fresh medium supplemented with tobramycin. We provide evidence that, although the transcriptional profile of P. aeruginosa is community agnostic, the transcriptomes of S. aureus and S. sanguinis are community aware. Furthermore, P. aeruginosa and P. melaninogenica are transcriptionally sensitive to the presence of mucin in ASM, whereas S. aureus and S. sanguinis largely do not alter their transcriptional profiles in the presence of mucin when grown in a community. Only P. aeruginosa shows a robust response to tobramycin. Genetic studies of mutants altered in community-specific growth provide complementary data regarding how these microbes adapt to a community context. IMPORTANCE Polymicrobial infections constitute the majority of infections in the cystic fibrosis (CF) airway, but their study has largely been neglected in a laboratory setting. Our lab previously reported a polymicrobial community that can help explain clinical outcomes in the lungs of persons with CF. Here, we obtained transcriptional profiles of the community versus monocultures to provide transcriptional information about how this model community responds to CF-related growth conditions and perturbations. Genetic studies provide complementary functional outputs to assess how the microbes adapt to life in a community.
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Affiliation(s)
- Christopher A. Kesthely
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Rendi R. Rogers
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Bassam El Hafi
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Fabrice Jean-Pierre
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - George A. O’Toole
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
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9
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Suo Z, Cummings DA, Puri AW, Schaefer AL, Greenberg EP. A Mesorhizobium japonicum quorum sensing circuit that involves three linked genes and an unusual acyl-homoserine lactone signal. mBio 2023; 14:e0101023. [PMID: 37227303 PMCID: PMC10470506 DOI: 10.1128/mbio.01010-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2023] [Accepted: 04/27/2023] [Indexed: 05/26/2023] Open
Abstract
Members of the genus Mesorhizobium, which are core components of the rhizosphere and specific symbionts of legume plants, possess genes for acyl-homoserine lactone (AHL) quorum sensing (QS). Here we show Mesorhizobium japonicum MAFF 303099 (formerly M. loti) synthesizes and responds to N-[(2E, 4E)-2,4-dodecadienoyl] homoserine lactone (2E, 4E-C12:2-HSL). We show that the 2E, 4E-C12:2-HSL QS circuit involves one of four luxR-luxI-type genes found in the sequenced genome of MAFF 303099. We refer to this circuit, which appears to be conserved among Mesorhizobium species, as R1-I1. We show that two other Mesorhizobium strains also produce 2E, 4E-C12:2-HSL. The 2E, 4E-C12:2-HSL is unique among known AHLs in its arrangement of two trans double bonds. The R1 response to 2E, 4E-C12:2-HSL is extremely selective in comparison with other LuxR homologs, and the trans double bonds appear critical for R1 signal recognition. Most well-studied LuxI-like proteins use S-adenosylmethionine and an acyl-acyl carrier protein as substrates for synthesis of AHLs. Others that form a subgroup of LuxI-type proteins use acyl-coenzyme A substrates rather than acyl-acyl carrier proteins. I1 clusters with the acyl-coenzyme A-type AHL synthases. We show that a gene linked to the I1 AHL synthase is involved in the production of the QS signal. The discovery of the unique I1 product enforces the view that further study of acyl-coenzyme A-dependent LuxI homologs will expand our knowledge of AHL diversity. The involvement of an additional enzyme in AHL generation leads us to consider this system a three-component QS circuit. IMPORTANCE We report a Mesorhizobium japonicum quorum sensing (QS) system involving a novel acyl-homoserine lactone (AHL) signal. This system is known to be involved in root nodule symbiosis with host plants. The chemistry of the newly described QS signal indicated that there may be a dedicated cellular enzyme involved in its synthesis in addition to the types known for production of other AHLs. Indeed, we report that an additional gene is required for synthesis of the unique signal, and we propose that this is a three-component QS circuit as opposed to the canonical two-component AHL QS circuits. The signaling system is exquisitely selective. The selectivity may be important when this species resides in the complex microbial communities around host plants and may make this system useful in various synthetic biology applications of QS circuits.
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Affiliation(s)
- Zehui Suo
- Integrative Microbiology Research Center, South China Agricultural University, Guangzhou, China
| | - Dale A. Cummings
- Department of Chemistry and the Henry Eyring Center for Cell and Genomes Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Aaron W. Puri
- Department of Chemistry and the Henry Eyring Center for Cell and Genomes Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Amy L. Schaefer
- Department of Microbiology, University of Washington, Seattle, Washington, USA
| | - E. Peter Greenberg
- Department of Microbiology, University of Washington, Seattle, Washington, USA
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10
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Kesthely CA, Rogers RR, Hafi BE, Jean-Pierre F, O’Toole GA. Transcriptional Profiling and Genetic Analysis of a Cystic Fibrosis Airway-Relevant Model Shows Asymmetric Responses to Growth in a Polymicrobial Community. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.24.542191. [PMID: 37293107 PMCID: PMC10245937 DOI: 10.1101/2023.05.24.542191] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Bacterial infections in the lungs of persons with cystic fibrosis are typically composed of multispecies biofilm-like communities, which modulate clinically relevant phenotypes that cannot be explained in the context of a single species culture. Most analyses to-date provide a picture of the transcriptional responses of individual pathogens, however, there is relatively little data describing the transcriptional landscape of clinically-relevant multispecies communities. Harnessing a previously described cystic fibrosis-relevant, polymicrobial community model consisting of Pseudomonas aeruginosa, Staphylococcus aureus, Streptococcus sanguinis and Prevotella melaninogenica , we performed an RNA-Seq analysis to elucidate the transcriptional profiles of the community grown in artificial sputum medium (ASM) as compared to growth in monoculture, without mucin, and in fresh medium supplemented with tobramycin. We provide evidence that, although the transcriptional profile of P. aeruginosa is community agnostic, the transcriptomes of S. aureus and S. sanguinis are community aware. Furthermore, P. aeruginosa and P. melaninogenica are transcriptionally sensitive to the presence of mucin in ASM, whereas S. aureus and S. sanguinis largely do not alter their transcriptional profiles in the presence of mucin when grown in a community. Only P. aeruginosa shows a robust response to tobramycin. Genetic studies of mutants altered in community-specific growth provide complementary data regarding how these microbes adapt to a community context. Importance Polymicrobial infections constitute the majority of infections in the cystic fibrosis (CF) airway, but their study has largely been neglected in a laboratory setting. Our lab previously reported a polymicrobial community that can explain clinical outcomes in the lungs of persons with CF. Here we obtain transcriptional profiles of the community versus monocultures to provide transcriptional information about how this model community responds to CF-related growth conditions and perturbations. Genetic studies provide complementary functional outputs to assess how the microbes adapt to life in a community.
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Affiliation(s)
| | - Rendi R. Rogers
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth
| | - Bassam El Hafi
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth
| | - Fabrice Jean-Pierre
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth
| | - George A. O’Toole
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth
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11
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Montelongo-Martínez LF, Hernández-Méndez C, Muriel-Millan LF, Hernández-Estrada R, Fabian-Del Olmo MJ, González-Valdez A, Soberón-Chávez G, Cocotl-Yañez M. Unraveling the regulation of pyocyanin synthesis by RsmA through MvaU and RpoS in Pseudomonas aeruginosa ID4365. J Basic Microbiol 2023; 63:51-63. [PMID: 36207285 DOI: 10.1002/jobm.202200432] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 09/05/2022] [Accepted: 09/18/2022] [Indexed: 01/04/2023]
Abstract
Pyocyanin is a phenazine with redox activity produced by Pseudomonas aeruginosa that is harmful to other bacteria and eukaryotic organisms by generating reactive oxygen species. Gene regulation of pyocyanin synthesis has been addressed in the PAO1 and PA14 strains and involves the three-quorum sensing systems Las, Rhl, and Pqs; the regulators RsaL, MvaU, and RpoS, and the posttranscriptional Rsm system, among others. Here, we determined how RsmA regulates pyocyanin synthesis in P. aeruginosa ID4365, an overproducer strain. We found that, in the protease peptone glucose ammonium salts medium, rsmA inactivation increases pyocyanin production compared with the wild-type strains ID4365, PAO, and PA14. We showed that RsmA regulates inversely the expression of both phz operons involved in pyocyanin synthesis; particularly the phz2 operon is positively regulated at the transcriptional level indirectly through MvaU. In addition, we found that the phz1 operon contributes mainly to pyocyanin synthesis and that RsmA negatively regulates phzM and phzS expression. Finally, we showed that translation of the sigma factor RpoS is positively regulated by RsmA, and the expression of rpoS under an independent promoter decreases pyocyanin production in the IDrsmA strain. These results indicate that RsmA regulates not only the genes for pyocyanin production but also their regulators.
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Affiliation(s)
- Luis F Montelongo-Martínez
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, México City, México
| | - Cristina Hernández-Méndez
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, México City, México
| | - Luis F Muriel-Millan
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México City, México
| | - René Hernández-Estrada
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, México City, México
| | - Misael J Fabian-Del Olmo
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, México City, México
| | - Abigail González-Valdez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México City, México
| | - Gloria Soberón-Chávez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México City, México
| | - Miguel Cocotl-Yañez
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, México City, México
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12
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Han X, Nan M, Cai X, Qiao B, Chen L, Shen L. Sennoside A inhibits quorum sensing system to attenuate its regulated virulence and pathogenicity via targeting LasR in Pseudomonas aeruginosa. Front Microbiol 2022; 13:1042214. [DOI: 10.3389/fmicb.2022.1042214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 10/12/2022] [Indexed: 11/06/2022] Open
Abstract
Pseudomonas aeruginosa is an important opportunistic pathogen, and the emergence of drug resistance greatly increased the difficulty of treating its infection. Cell density-dependent quorum sensing (QS) system not only regulates the virulence but also associates with the drug resistance of P. aeruginosa. Screening for agents targeting QS to inhibit bacterial virulence and pathogenicity is considered a promising strategy to combat P. aeruginosa infection. In the present study, sennoside A was found to be able to inhibit the QS expression of P. aeruginosa at subinhibitory concentrations. The QS-regulated virulence factors, including protease, elastase, rhamnolipid, and pyocyanin, were also inhibited by sennoside A at both transcriptional and translational levels. Moreover, sennoside A could suppress the motility of twitching, swimming, and swarming as well as the biofilm formation, which is associated with the acute and chronic infections of P. aeruginosa in a dose-dependent manner. The attenuated pathogenicity of P. aeruginosa by sennoside A was further verified by Chinese cabbage, Drosophila melanogaster, and Caenorhabditis elegans infection analysis. Further study found that sennoside A might target the las system, mainly LasR, to interfere with QS. All the results indicate that sennoside A could inhibit the QS system to attenuate its regulated virulence and pathogenicity via mainly targeting LasR in P. aeruginosa and further research to identify its anti-QS activity for other Gram-negative bacteria is warranted.
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13
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Soto-Aceves MP, González-Valdez A, Cocotl-Yañez M, Soberón-Chávez G. Pseudomonas aeruginosa LasR overexpression leads to a RsaL-independent pyocyanin production inhibition in a low phosphate condition. MICROBIOLOGY (READING, ENGLAND) 2022; 168. [PMID: 36301076 DOI: 10.1099/mic.0.001262] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Several Pseudomonas aeruginosa virulence-related traits like pyocyanin are regulated by an intricate regulatory network called quorum sensing (QS) that relies on transcriptional regulators that are activated through binding to a self-produced molecule called an autoinducer (AI). QS is composed of three systems, Las, Rhl and Pqs. In the Las system, the regulatory protein LasR interacts with its AI to activate the other two QS systems. In turn, the Rhl and Pqs systems regulate the expression of multiple virulence-related genes, such as the genes of the reiterated operons phzA1B1C1D1E1F1G1 and phzA2B2C2D2E2F2G2 involved in pyocyanin production. The Las system also regulates the negative regulator RsaL, which provides negative feedback to the QS-response, including repression of pyocyanin synthesis genes. In this work, we describe that LasR can act as a negative regulator of phzA1 transcription and hence of pyocyanin production and that this regulation is independent of RsaL activity. This work contributes to the understanding of QS-dependent pyocyanin production and demonstrates a previously uncharacterized role of LasR as a repressor.
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Affiliation(s)
- Martín Paolo Soto-Aceves
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico.,Present address: Department of Microbiology, University of Washington, Seattle, Washington, USA
| | - Abigail González-Valdez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Miguel Cocotl-Yañez
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico
| | - Gloria Soberón-Chávez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Mexico City, Mexico
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14
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Hills OJ, Yong CW, Scott AJ, Devine DA, Smith J, Chappell HF. Atomic-scale interactions between quorum sensing autoinducer molecules and the mucoid P. aeruginosa exopolysaccharide matrix. Sci Rep 2022; 12:7724. [PMID: 35545629 PMCID: PMC9095684 DOI: 10.1038/s41598-022-11499-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 04/18/2022] [Indexed: 12/22/2022] Open
Abstract
Mucoid Pseudomonas aeruginosa is a prevalent cystic fibrosis (CF) lung coloniser whose chronicity is associated with the formation of cation cross-linked exopolysaccharide (EPS) matrices, which form a biofilm that acts as a diffusion barrier, sequestering cationic and neutral antimicrobials, and making it extremely resistant to pharmacological challenge. Biofilm chronicity and virulence of the colony is regulated by quorum sensing autoinducers (QSAIs), small signalling metabolites that pass between bacteria, through the biofilm matrix, regulating genetic responses on a population-wide scale. The nature of how these molecules interact with the EPS is poorly understood, despite the fact that they must pass through EPS matrix to reach neighbouring bacteria. Interactions at the atomic-scale between two QSAI molecules, C4-HSL and PQS—both utilised by mucoid P. aeruginosa in the CF lung—and the EPS, have been studied for the first time using a combined molecular dynamics (MD) and density functional theory (DFT) approach. A large-scale, calcium cross-linked, multi-chain EPS molecular model was developed and MD used to sample modes of interaction between QSAI molecules and the EPS that occur at physiological equilibrium. The thermodynamic stability of the QSAI-EPS adducts were calculated using DFT. These simulations provide a thermodynamic rationale for the apparent free movement of C4-HSL, highlight key molecular functionality responsible for EPS binding and, based on its significantly reduced mobility, suggest PQS as a viable target for quorum quenching.
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Affiliation(s)
- Oliver J Hills
- School of Food Science & Nutrition, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.
| | - Chin W Yong
- Daresbury Laboratory, Scientific Computing Department, Science and Technology Facilities Council, Keckwick Lane, Daresbury, Warrington, WA4 4AD, UK.,Division of Pharmacy and Optometry, School of Health Sciences, University of Manchester, Oxford Road, Manchester, M13 9PL, UK
| | - Andrew J Scott
- School of Chemical & Process Engineering, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Deirdre A Devine
- School of Dentistry, University of Leeds, Clarendon Way, Leeds, LS2 9LU, UK
| | - James Smith
- School of Food Science & Nutrition, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK
| | - Helen F Chappell
- School of Food Science & Nutrition, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK.
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15
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Mould DL, Stevanovic M, Ashare A, Schultz D, Hogan DA. Metabolic basis for the evolution of a common pathogenic Pseudomonas aeruginosa variant. eLife 2022; 11:e76555. [PMID: 35502894 PMCID: PMC9224983 DOI: 10.7554/elife.76555] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Accepted: 04/24/2022] [Indexed: 11/21/2022] Open
Abstract
Microbes frequently evolve in reproducible ways. Here, we show that differences in specific metabolic regulation rather than inter-strain interactions explain the frequent presence of lasR loss-of-function (LOF) mutations in the bacterial pathogen Pseudomonas aeruginosa. While LasR contributes to virulence through its role in quorum sensing, lasR mutants have been associated with more severe disease. A model based on the intrinsic growth kinetics for a wild type strain and its LasR- derivative, in combination with an experimental evolution based genetic screen and further genetics analyses, indicated that differences in metabolism were sufficient to explain the rise of these common mutant types. The evolution of LasR- lineages in laboratory and clinical isolates depended on activity of the two-component system CbrAB, which modulates substrate prioritization through the catabolite repression control pathway. LasR- lineages frequently arise in cystic fibrosis lung infections and their detection correlates with disease severity. Our analysis of bronchoalveolar lavage fluid metabolomes identified compounds that negatively correlate with lung function, and we show that these compounds support enhanced growth of LasR- cells in a CbrB-controlled manner. We propose that in vivo metabolomes contribute to pathogen evolution, which may influence the progression of disease and its treatment.
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Affiliation(s)
- Dallas L Mould
- Department of Microbiology and Immunology, Geisel School of Medicine at DartmouthHanoverUnited States
| | - Mirjana Stevanovic
- Department of Microbiology and Immunology, Geisel School of Medicine at DartmouthHanoverUnited States
| | - Alix Ashare
- Department of Microbiology and Immunology, Geisel School of Medicine at DartmouthHanoverUnited States
- Department of Medicine, Dartmouth-Hitchock Medical CenterLebanonUnited States
| | - Daniel Schultz
- Department of Microbiology and Immunology, Geisel School of Medicine at DartmouthHanoverUnited States
| | - Deborah A Hogan
- Department of Microbiology and Immunology, Geisel School of Medicine at DartmouthHanoverUnited States
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16
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Wellington Miranda S, Cong Q, Schaefer AL, MacLeod EK, Zimenko A, Baker D, Greenberg EP. A covariation analysis reveals elements of selectivity in quorum sensing systems. eLife 2021; 10:69169. [PMID: 34180398 PMCID: PMC8328516 DOI: 10.7554/elife.69169] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Accepted: 06/25/2021] [Indexed: 12/14/2022] Open
Abstract
Many bacteria communicate with kin and coordinate group behaviors through a form of cell-cell signaling called acyl-homoserine lactone (AHL) quorum sensing (QS). In these systems, a signal synthase produces an AHL to which its paired receptor selectively responds. Selectivity is fundamental to cell signaling. Despite its importance, it has been challenging to determine how this selectivity is achieved and how AHL QS systems evolve and diversify. We hypothesized that we could use covariation within the protein sequences of AHL synthases and receptors to identify selectivity residues. We began by identifying about 6000 unique synthase-receptor pairs. We then used the protein sequences of these pairs to identify covariation patterns and mapped the patterns onto the LasI/R system from Pseudomonas aeruginosa PAO1. The covarying residues in both proteins cluster around the ligand-binding sites. We demonstrate that these residues are involved in system selectivity toward the cognate signal and go on to engineer the Las system to both produce and respond to an alternate AHL signal. We have thus demonstrated that covariation methods provide a powerful approach for investigating selectivity in protein-small molecule interactions and have deepened our understanding of how communication systems evolve and diversify.
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Affiliation(s)
| | - Qian Cong
- Department of Biochemistry, University of Washington, Seattle, United States.,Institute for Protein Design, University of Washington, Seattle, United States.,Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, United States.,Department of Biophysics, University of Texas Southwestern Medical Center, Dallas, United States
| | - Amy L Schaefer
- Department of Microbiology, University of Washington, Seattle, United States
| | - Emily Kenna MacLeod
- Department of Microbiology, University of Washington, Seattle, United States
| | - Angelina Zimenko
- Department of Microbiology, University of Washington, Seattle, United States
| | - David Baker
- Department of Biochemistry, University of Washington, Seattle, United States.,Institute for Protein Design, University of Washington, Seattle, United States.,Howard Hughes Medical Institute, University of Washington, Seattle, United States
| | - E Peter Greenberg
- Department of Microbiology, University of Washington, Seattle, United States
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17
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The Rhl Quorum-Sensing System Is at the Top of the Regulatory Hierarchy under Phosphate-Limiting Conditions in Pseudomonas aeruginosa PAO1. J Bacteriol 2021; 203:JB.00475-20. [PMID: 33288622 DOI: 10.1128/jb.00475-20] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 12/02/2020] [Indexed: 12/13/2022] Open
Abstract
Pseudomonas aeruginosa is a major nosocomial pathogen that presents high-level resistance to antibiotics. Its ability to cause infections relies on the production of multiple virulence factors. Quorum sensing (QS) regulates the expression of many of these virulence factors through three QS systems: Las, Rhl, and PQS. The Las system positively regulates the other two systems, so it is at the top of a hierarchized regulation. Nevertheless, clinical and environmental strains that lack a functional Las system have been isolated, and, surprisingly, some of them still have the ability to produce virulence factors and infect animal models, so it has been suggested that the hierarchy is flexible under some conditions or with atypical strains. Here, we analyze the PAO1 type strain and its ΔlasR-derived mutant and report, for the first time, a growth condition (phosphate limitation) where LasR absence has no effect either on virulence factor production or on the gene expression profile, in contrast to a condition of phosphate repletion where the LasR hierarchy is maintained. This work provides evidence on how the QS hierarchy can change from being a strictly LasR-dependent to a LasR-independent RhlR-based hierarchy under phosphate limitation even in the PAO1 type strain.IMPORTANCE Pseudomonas aeruginosa is an important pathogen, considered a priority for the development of new therapeutic strategies. An important approach to fight its infections relies on blocking quorum sensing. The Las system is the main regulator of the quorum-sensing response, so many research efforts aim to block this system to suppress the entire response. In this work, we show that LasR is dispensable in a phosphate-limited environment in the PAO1 type strain, which has been used to define the quorum-sensing response hierarchy, and that under this condition RhlR is at the top of the regulation hierarchy. These results are highly significant, since phosphate limitation represents a similar environment to the one that P. aeruginosa faces when establishing infections.
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18
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Beasley KL, Cristy SA, Elmassry MM, Dzvova N, Colmer-Hamood JA, Hamood AN. During bacteremia, Pseudomonas aeruginosa PAO1 adapts by altering the expression of numerous virulence genes including those involved in quorum sensing. PLoS One 2020; 15:e0240351. [PMID: 33057423 PMCID: PMC7561203 DOI: 10.1371/journal.pone.0240351] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 09/24/2020] [Indexed: 12/17/2022] Open
Abstract
Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that produces numerous virulence factors and causes serious infections in trauma patients and patients with severe burns. We previously showed that the growth of P. aeruginosa in blood from severely burned or trauma patients altered the expression of numerous genes. However, the specific influence of whole blood from healthy volunteers on P. aeruginosa gene expression is not known. Transcriptome analysis of P. aeruginosa grown for 4 h in blood from healthy volunteers compared to that when grown in laboratory medium revealed that the expression of 1085 genes was significantly altered. Quorum sensing (QS), QS-related, and pyochelin synthesis genes were downregulated, while genes of the type III secretion system and those for pyoverdine synthesis were upregulated. The observed effect on the QS and QS-related genes was shown to reside within serum fraction: growth of PAO1 in the presence of 10% human serum from healthy volunteers significantly reduced the expression of QS and QS-regulated genes at 2 and 4 h of growth but significantly enhanced their expression at 8 h. Additionally, the production of QS-regulated virulence factors, including LasA and pyocyanin, was also influenced by the presence of human serum. Serum fractionation experiments revealed that part of the observed effect resides within the serum fraction containing <10-kDa proteins. Growth in serum reduced the production of many PAO1 outer membrane proteins but enhanced the production of others including OprF, a protein previously shown to play a role in the regulation of QS gene expression. These results suggest that factor(s) within human serum: 1) impact P. aeruginosa pathogenesis by influencing the expression of different genes; 2) differentially regulate the expression of QS and QS-related genes in a growth phase- or time-dependent mechanism; and 3) manipulate the production of P. aeruginosa outer membrane proteins.
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Affiliation(s)
- Kellsie L. Beasley
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, Texas, Untied States of America
| | - Shane A. Cristy
- Honors College, Texas Tech University, Lubbock, Texas, Untied States of America
| | - Moamen M. Elmassry
- Department of Biological Sciences, Texas Tech University, Lubbock, Texas, Untied States of America
| | - Nyaradzo Dzvova
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, Texas, Untied States of America
| | - Jane A. Colmer-Hamood
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, Texas, Untied States of America
- Department of Medical Education, Texas Tech University Health Sciences Center, Lubbock, Texas, Untied States of America
| | - Abdul N. Hamood
- Department of Immunology and Molecular Microbiology, Texas Tech University Health Sciences Center, Lubbock, Texas, Untied States of America
- Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, Texas, Untied States of America
- * E-mail:
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19
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Pip serves as an intermediate in RpoS-modulated phz2 expression and pyocyanin production in Pseudomonas aeruginosa. Microb Pathog 2020; 147:104409. [PMID: 32707314 DOI: 10.1016/j.micpath.2020.104409] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Revised: 07/17/2020] [Accepted: 07/17/2020] [Indexed: 11/22/2022]
Abstract
Pyocyanin, a main virulence factor that is produced by Pseudomonas aeruginosa, plays an important role in pathogen-host interaction during infection. Two copies of phenazine-biosynthetic operons on genome, phz1 (phzA1B1C1D1E1F1G1) and phz2 (phzA2B2C2D2E2F2G2), contribute to phenazine biosynthesis. In our previous study, we found that RpoS positively regulates expression of the phz2 operon and pyocyanin biosynthesis in P. aeruginosa PAO1. In this work, when a TetR-family regulator gene, pip, was knocked out, we found that pyocyanin production was dramatically reduced, indicating that Pip positively regulates pyocyanin biosynthesis. With further phenazines quantification and β-galactosidase assay, we confirmed that Pip positively regulates phz2 expression, but does not regulate phz1 expression. In addition, while the rpoS gene was deleted, expression of pip was down-regulated. Expression of rpoS in the wild-type PAO1 strain, however, was similar to that in the Pip-deficient mutant PAΔpip, suggesting that expression of pip could positively be regulated by RpoS, whereas rpoS could not be regulated by Pip. Taken together, we drew a conclusion that Pip might serve as an intermediate in RpoS-modulated expression of the phz2 operon and pyocyanin biosynthesis in P. aeruginosa.
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20
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Chatterjee P, Sass G, Swietnicki W, Stevens DA. Review of Potential Pseudomonas Weaponry, Relevant to the Pseudomonas-Aspergillus Interplay, for the Mycology Community. J Fungi (Basel) 2020; 6:jof6020081. [PMID: 32517271 PMCID: PMC7345761 DOI: 10.3390/jof6020081] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Revised: 06/03/2020] [Accepted: 06/03/2020] [Indexed: 12/15/2022] Open
Abstract
Pseudomonas aeruginosa is one of the most prominent opportunistic bacteria in airways of cystic fibrosis patients and in immunocompromised patients. These bacteria share the same polymicrobial niche with other microbes, such as the opportunistic fungus Aspergillus fumigatus. Their inter-kingdom interactions and diverse exchange of secreted metabolites are responsible for how they both fare in competition for ecological niches. The outcomes of their contests likely determine persistent damage and degeneration of lung function. With a myriad of virulence factors and metabolites of promising antifungal activity, P. aeruginosa products or their derivatives may prove useful in prophylaxis and therapy against A. fumigatus. Quorum sensing underlies the primary virulence strategy of P. aeruginosa, which serves as cell–cell communication and ultimately leads to the production of multiple virulence factors. Understanding the quorum-sensing-related pathogenic mechanisms of P. aeruginosa is a first step for understanding intermicrobial competition. In this review, we provide a basic overview of some of the central virulence factors of P. aeruginosa that are regulated by quorum-sensing response pathways and briefly discuss the hitherto known antifungal properties of these virulence factors. This review also addresses the role of the bacterial secretion machinery regarding virulence factor secretion and maintenance of cell–cell communication.
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Affiliation(s)
- Paulami Chatterjee
- California Institute for Medical Research, San Jose, CA 95128, USA; (P.C.); (G.S.)
| | - Gabriele Sass
- California Institute for Medical Research, San Jose, CA 95128, USA; (P.C.); (G.S.)
| | - Wieslaw Swietnicki
- Department of Immunology of Infectious Diseases, Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, 50-114 Wroclaw, Poland;
| | - David A. Stevens
- California Institute for Medical Research, San Jose, CA 95128, USA; (P.C.); (G.S.)
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
- Correspondence: ; Tel.: +1-408-998-4554
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21
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Abstract
Pseudomonas aeruginosa is a versatile bacterium found in various environments. It can cause severe infections in immunocompromised patients and naturally resists many antibiotics. The World Health Organization listed it among the top priority pathogens for research and development of new antimicrobial compounds. Quorum sensing (QS) is a cell-cell communication mechanism, which is important for P. aeruginosa adaptation and pathogenesis. Here, we validate the central role of the PqsE protein in QS particularly by its impact on the regulator RhlR. This study challenges the traditional dogmas of QS regulation in P. aeruginosa and ties loose ends in our understanding of the traditional QS circuit by confirming RhlR to be the main QS regulator in P. aeruginosa. PqsE could represent an ideal target for the development of new control methods against the virulence of P. aeruginosa. This is especially important when considering that LasR-defective mutants frequently arise, e.g., in chronic infections. The bacterium Pseudomonas aeruginosa has emerged as a central threat in health care settings and can cause a large variety of infections. It expresses an arsenal of virulence factors and a diversity of survival functions, many of which are finely and tightly regulated by an intricate circuitry of three quorum sensing (QS) systems. The las system is considered at the top of the QS hierarchy and activates the rhl and pqs systems. It is composed of the LasR transcriptional regulator and the LasI autoinducer synthase, which produces 3-oxo-C12-homoserine lactone (3-oxo-C12-HSL), the ligand of LasR. RhlR is the transcriptional regulator for the rhl system and is associated with RhlI, which produces its cognate autoinducer C4-HSL. The third QS system is composed of the pqsABCDE operon and the MvfR (PqsR) regulator. PqsABCD synthetize 4-hydroxy-2-alkylquinolines (HAQs), which include ligands activating MvfR. PqsE is not required for HAQ production and instead is associated with the expression of genes controlled by the rhl system. While RhlR is often considered the main regulator of rhlI, we confirmed that LasR is in fact the principal regulator of C4-HSL production and that RhlR regulates rhlI and production of C4-HSL essentially only in the absence of LasR by using liquid chromatography-mass spectrometry quantifications and gene expression reporters. Investigating the expression of RhlR targets also clarified that activation of RhlR-dependent QS relies on PqsE, especially when LasR is not functional. This work positions RhlR as the key QS regulator and points to PqsE as an essential effector for full activation of this regulation. IMPORTANCEPseudomonas aeruginosa is a versatile bacterium found in various environments. It can cause severe infections in immunocompromised patients and naturally resists many antibiotics. The World Health Organization listed it among the top priority pathogens for research and development of new antimicrobial compounds. Quorum sensing (QS) is a cell-cell communication mechanism, which is important for P. aeruginosa adaptation and pathogenesis. Here, we validate the central role of the PqsE protein in QS particularly by its impact on the regulator RhlR. This study challenges the traditional dogmas of QS regulation in P. aeruginosa and ties loose ends in our understanding of the traditional QS circuit by confirming RhlR to be the main QS regulator in P. aeruginosa. PqsE could represent an ideal target for the development of new control methods against the virulence of P. aeruginosa. This is especially important when considering that LasR-defective mutants frequently arise, e.g., in chronic infections.
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22
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Mukherji R, Zhang S, Chowdhury S, Stallforth P. Chimeric LuxR Transcription Factors Rewire Natural Product Regulation. Angew Chem Int Ed Engl 2020; 59:6192-6195. [PMID: 31943579 PMCID: PMC7187462 DOI: 10.1002/anie.201914449] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Revised: 12/12/2019] [Indexed: 01/17/2023]
Abstract
LuxR-type transcriptional activator proteins frequently regulate the expression of biosynthetic gene clusters (BGCs). With only a fraction of bacterial BGCs being expressed under standard culturing conditions, modulation of LuxRs would provide a powerful approach to activate silent clusters. We show that by exploiting the modular nature of LuxR proteins, it is possible to construct functional chimeric LuxRs, which enables both the rewiring of quorum sensing systems and the activation of silent BGCs. Importantly, our strategy allowed us to identify the novel natural product pseudomonol from a bacterium of the genus Pseudomonas.
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Affiliation(s)
- Ruchira Mukherji
- Independent Junior Research Group Chemistry of Microbial CommunicationLeibniz Institute for Natural Product Research and Infection BiologyHans Knöll Institute (HKI)Beutenbergstrasse 11a07745JenaGermany
| | - Shuaibing Zhang
- Independent Junior Research Group Chemistry of Microbial CommunicationLeibniz Institute for Natural Product Research and Infection BiologyHans Knöll Institute (HKI)Beutenbergstrasse 11a07745JenaGermany
| | - Somak Chowdhury
- Independent Junior Research Group Chemistry of Microbial CommunicationLeibniz Institute for Natural Product Research and Infection BiologyHans Knöll Institute (HKI)Beutenbergstrasse 11a07745JenaGermany
| | - Pierre Stallforth
- Independent Junior Research Group Chemistry of Microbial CommunicationLeibniz Institute for Natural Product Research and Infection BiologyHans Knöll Institute (HKI)Beutenbergstrasse 11a07745JenaGermany
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23
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Mukherji R, Zhang S, Chowdhury S, Stallforth P. Chimeric LuxR Transcription Factors Rewire Natural Product Regulation. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201914449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Ruchira Mukherji
- Independent Junior Research Group Chemistry of Microbial CommunicationLeibniz Institute for Natural Product Research and Infection BiologyHans Knöll Institute (HKI) Beutenbergstrasse 11a 07745 Jena Germany
| | - Shuaibing Zhang
- Independent Junior Research Group Chemistry of Microbial CommunicationLeibniz Institute for Natural Product Research and Infection BiologyHans Knöll Institute (HKI) Beutenbergstrasse 11a 07745 Jena Germany
| | - Somak Chowdhury
- Independent Junior Research Group Chemistry of Microbial CommunicationLeibniz Institute for Natural Product Research and Infection BiologyHans Knöll Institute (HKI) Beutenbergstrasse 11a 07745 Jena Germany
| | - Pierre Stallforth
- Independent Junior Research Group Chemistry of Microbial CommunicationLeibniz Institute for Natural Product Research and Infection BiologyHans Knöll Institute (HKI) Beutenbergstrasse 11a 07745 Jena Germany
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24
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Shah N, Gislason AS, Becker M, Belmonte MF, Fernando WGD, de Kievit TR. Investigation of the quorum-sensing regulon of the biocontrol bacterium Pseudomonas chlororaphis strain PA23. PLoS One 2020; 15:e0226232. [PMID: 32109244 PMCID: PMC7048289 DOI: 10.1371/journal.pone.0226232] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 02/12/2020] [Indexed: 12/15/2022] Open
Abstract
Pseudomonas chlororaphis strain PA23 is a biocontrol agent capable of protecting canola from stem rot disease caused by the fungal pathogen Sclerotinia sclerotiorum. PA23 produces several inhibitory compounds that are under control of a complex regulatory network. Included in this cascade is the PhzRI quorum sensing (QS) system, which plays an essential role in PA23 biocontrol, as well as CsaRI and AurRI, which have not yet been characterized in PA23. The focus of the current study was to employ RNA sequencing to explore the spectrum of PA23 genes under QS control. In this work, we investigated genes under the control of the main QS transcriptional regulator, PhzR, as well as those differentially expressed in an AHL-deficient strain, PA23-6863, which constitutively expresses an AiiA lactonase, rendering the strain QS defective. Transcriptomic profiling revealed 545 differentially expressed genes (365 downregulated; 180 upregulated) in the phzR mutant and 534 genes (382 downregulated; 152 upregulated) in the AHL-deficient PA23-6863. In both strains, decreased expression of phenazine, pyrrolnitrin, and exoprotease biosynthetic genes was observed. We have previously reported that QS activates expression of these genes and their encoded products. In addition, elevated siderophore and decreased chitinase gene expression was observed in the QS-deficient stains, which was confirmed by phenotypic analysis. Inspection of the promoter regions revealed the presence of "phz-box" sequences in only 58 of the 807 differentially expressed genes, suggesting that much of the QS regulon is indirectly regulated. Consistent with this notion, 41 transcriptional regulators displayed altered expression in one or both of the QS-deficient strains. Collectively, our findings indicate that QS governs expression of approximately 13% of the PA23 genome affecting diverse functions ranging from secondary metabolite production to general metabolism.
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Affiliation(s)
- Nidhi Shah
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - April S. Gislason
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Michael Becker
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Mark F. Belmonte
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | | | - Teresa R. de Kievit
- Department of Microbiology, University of Manitoba, Winnipeg, Manitoba, Canada
- * E-mail:
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García-Reyes S, Soberón-Chávez G, Cocotl-Yanez M. The third quorum-sensing system of Pseudomonas aeruginosa: Pseudomonas quinolone signal and the enigmatic PqsE protein. J Med Microbiol 2020; 69:25-34. [PMID: 31794380 DOI: 10.1099/jmm.0.001116] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Pseudomonas aeruginosa is an opportunistic pathogen that produces several virulence factors such as lectin A, pyocyanin, elastase and rhamnolipids. These compounds are controlled transcriptionally by three quorum-sensing circuits, two based on the synthesis and detection of N-acyl-homoserine-lactone termed the Las and Rhl system and a third system named the Pseudomonas quinolone signal (PQS) system, which is responsible for generating 2-alkyl-4(1 h)-quinolones (AQs). The transcriptional regulator called PqsR binds to the promoter of pqsABCDE in the presence of PQS or HHQ creating a positive feedback-loop. PqsE, encoded in the operon for AQ synthesis, is a crucial protein for pyocyanin production, activating the Rhl system by a still not fully understood mechanism. In turn, the regulation of the PQS system is modulated by Las and Rhl systems, which act positively and negatively, respectively. This review focuses on the PQS system, from its discovery to its role in Pseudomonas pathogenesis, such as iron depletion and pyocyanin synthesis that involves the PqsE protein - an intriguing player of this system.
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Affiliation(s)
- Selene García-Reyes
- Departamento de Biología molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Apdo Postal 70228, C.P. 04510, Ciudad de México, Mexico
| | - Gloria Soberón-Chávez
- Departamento de Biología molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ciudad Universitaria, Apdo Postal 70228, C.P. 04510, Ciudad de México, Mexico
| | - Miguel Cocotl-Yanez
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México. Av. Universidad 3000, Cd. Universitaria, C.P. 04510, Coyoacán, Ciudad de México, Mexico
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Crocker AW, Harty CE, Hammond JH, Willger SD, Salazar P, Botelho NJ, Jacobs NJ, Hogan DA. Pseudomonas aeruginosa Ethanol Oxidation by AdhA in Low-Oxygen Environments. J Bacteriol 2019; 201:e00393-19. [PMID: 31527114 PMCID: PMC6832066 DOI: 10.1128/jb.00393-19] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 09/11/2019] [Indexed: 12/26/2022] Open
Abstract
Pseudomonas aeruginosa has a broad metabolic repertoire that facilitates its coexistence with different microbes. Many microbes secrete products that P. aeruginosa can then catabolize, including ethanol, a common fermentation product. Here, we show that under oxygen-limiting conditions P. aeruginosa utilizes AdhA, an NAD-linked alcohol dehydrogenase, as a previously undescribed means for ethanol catabolism. In a rich medium containing ethanol, AdhA, but not the previously described PQQ-linked alcohol dehydrogenase, ExaA, oxidizes ethanol and leads to the accumulation of acetate in culture supernatants. AdhA-dependent acetate accumulation and the accompanying decrease in pH promote P. aeruginosa survival in LB-grown stationary-phase cultures. The transcription of adhA is elevated by hypoxia and under anoxic conditions, and we show that it is regulated by the Anr transcription factor. We have shown that lasR mutants, which lack an important quorum sensing regulator, have higher levels of Anr-regulated transcripts under low-oxygen conditions than their wild-type counterparts. Here, we show that a lasR mutant, when grown with ethanol, has an even larger decrease in pH than the wild type (WT) that is dependent on both anr and adhA The large increase in AdhA activity is similar to that of a strain expressing a hyperactive Anr-D149A variant. Ethanol catabolism in P. aeruginosa by AdhA supports growth on ethanol as a sole carbon source and electron donor in oxygen-limited settings and in cells growing by denitrification under anoxic conditions. This is the first demonstration of a physiological role for AdhA in ethanol oxidation in P. aeruginosaIMPORTANCE Ethanol is a common product of microbial fermentation, and the Pseudomonas aeruginosa response to and utilization of ethanol are relevant to our understanding of its role in microbial communities. Here, we report that the putative alcohol dehydrogenase AdhA is responsible for ethanol catabolism and acetate accumulation under low-oxygen conditions and that it is regulated by Anr.
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Affiliation(s)
- Alex W Crocker
- Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Colleen E Harty
- Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - John H Hammond
- Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Sven D Willger
- Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Pedro Salazar
- Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Nico J Botelho
- Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Nicholas J Jacobs
- Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
| | - Deborah A Hogan
- Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA
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The Pseudomonas aeruginosa Orphan Quorum Sensing Signal Receptor QscR Regulates Global Quorum Sensing Gene Expression by Activating a Single Linked Operon. mBio 2018; 9:mBio.01274-18. [PMID: 30154259 PMCID: PMC6113619 DOI: 10.1128/mbio.01274-18] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Pseudomonas aeruginosa uses two acyl-homoserine lactone signals and two quorum sensing (QS) transcription factors, LasR and RhlR, to activate dozens of genes. LasR responds to N-3-oxo-dodecanoyl-homoserine lactone (3OC12-HSL) and RhlR to N-butanoyl-homoserine lactone (C4-HSL). There is a third P. aeruginosa acyl-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 in P. aeruginosa QS, we performed a chromatin immunoprecipitation analysis, which showed this transcription factor bound the promoter of only a single operon of three genes linked to qscR, 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. Quorum 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 bacterium Pseudomonas aeruginosa has a particularly complicated quorum sensing system involving multiple signals and receptors. One of these receptors, QscR, downregulates gene expression, unlike the other receptors in P. 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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Higgins S, Heeb S, Rampioni G, Fletcher MP, Williams P, Cámara M. Differential Regulation of the Phenazine Biosynthetic Operons by Quorum Sensing in Pseudomonas aeruginosa PAO1-N. Front Cell Infect Microbiol 2018; 8:252. [PMID: 30083519 PMCID: PMC6064868 DOI: 10.3389/fcimb.2018.00252] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 07/03/2018] [Indexed: 01/26/2023] Open
Abstract
The Pseudomonas aeruginosa quorum sensing (QS) network plays a key role in the adaptation to environmental changes and the control of virulence factor production in this opportunistic human pathogen. Three interlinked QS systems, namely las, rhl, and pqs, are central to the production of pyocyanin, a phenazine virulence factor which is typically used as phenotypic marker for analysing QS. Pyocyanin production in P. aeruginosa is a complex process involving two almost identical operons termed phzA1B1C1D1E1F1G1 (phz1) and phzA2B2C2D2E2F2G2 (phz2), which drive the production of phenazine-1-carboxylic acid (PCA) which is further converted to pyocyanin by two modifying enzymes PhzM and PhzS. Due to the high sequence conservation between the phz1 and phz2 operons (nucleotide identity > 98%), analysis of their individual expression by RNA hybridization, qRT-PCR or transcriptomics is challenging. To overcome this difficulty, we utilized luminescence based promoter fusions of each phenazine operon to measure in planktonic cultures their transcriptional activity in P. aeruginosa PAO1-N genetic backgrounds impaired in different components of the las, rhl, and pqs QS systems, in the presence or absence of different QS signal molecules. Using this approach, we found that all three QS systems play a role in differentially regulating the phz1 and phz2 phenazine operons, thus uncovering a higher level of complexity to the QS regulation of PCA biosynthesis in P. aeruginosa than previously appreciated. Importance The way the P. aeruginosa QS regulatory networks are intertwined creates a challenge when analysing the mechanisms governing specific QS-regulated traits. Multiple QS regulators and signals have been associated with the production of phenazine virulence factors. In this work we designed experiments where we dissected the contribution of specific QS switches using individual mutations and complementation strategies to gain further understanding of the specific roles of these QS elements in controlling expression of the two P. aeruginosa phenazine operons. Using this approach we have teased out which QS regulators have either indirect or direct effects on the regulation of the two phenazine biosynthetic operons. The data obtained highlight the sophistication of the QS cascade in P. aeruginosa and the challenges in analysing the control of phenazine secondary metabolites.
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Affiliation(s)
- Steven Higgins
- Centre for Biomolecular Science, School of Life Science, University of Nottingham, Nottingham, United Kingdom
- Department of Plant and Microbial Biology, University of Zürich, Zurich, Switzerland
| | - Stephan Heeb
- Centre for Biomolecular Science, School of Life Science, University of Nottingham, Nottingham, United Kingdom
| | - Giordano Rampioni
- Centre for Biomolecular Science, School of Life Science, University of Nottingham, Nottingham, United Kingdom
- Department of Science, University Roma Tre, Rome, Italy
| | - Mathew P. Fletcher
- Centre for Biomolecular Science, School of Life Science, University of Nottingham, Nottingham, United Kingdom
| | - Paul Williams
- Centre for Biomolecular Science, School of Life Science, University of Nottingham, Nottingham, United Kingdom
| | - Miguel Cámara
- Centre for Biomolecular Science, School of Life Science, University of Nottingham, Nottingham, United Kingdom
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Chowdhury N, Bagchi A. Identification of ligand binding activity and DNA recognition by RhlR protein from opportunistic pathogen Pseudomonas aeruginosa-a molecular dynamic simulation approach. J Mol Recognit 2018; 31:e2738. [PMID: 29968257 DOI: 10.1002/jmr.2738] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2017] [Revised: 05/21/2018] [Accepted: 06/01/2018] [Indexed: 11/07/2022]
Abstract
RhlR protein from opportunistic pathogen Pseudomonas aeruginosa is involved in the transcription of virulence genes of the organism. The RhlR protein functions as a dimer and binds to the cognate promoter DNA with the help of an autoinducer ligand BHL to initiate the transcription of the virulence genes. Till date, there are no reports that detail the mechanism of virulence gene expression by RhlR protein in P. aeruginosa. In this work, we tried to analyse the molecular aspects of the various binding interactions of the RhlR protein while formimg the dimmer as well as with the promoter DNA. We analysed the mode of dimerisation of the RhlR protein and its binding interactions with the autoinducer BHL ligand. From our analyses, we could identify the potential amino acid residues which are involved in the binding interactions. We also predicted how the autoinducer BHL would help in making contacts with the DNA as well as with itself. Thus, the autoinducer BHL would serve as an important mediator of molecular interactions involved in binding the RhlR protein to itself as well as with the promoter DNA. Therefore, any other molecule which would be able to compete with the autoinducer ligand BHL to bind to RhlR protein but would not let the RhlR protein bind the promoter DNA would be an ideal drug candidate to prevent the transcription process of the virulence genes in P. aeruginosa. Our future aim is to predict suitable ligands which would compete with BHL to thwart the transcription process.
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Affiliation(s)
- Nilkanta Chowdhury
- Department of Biochemistry and Biophysics, University of Kalyani, Nadia, India
| | - Angshuman Bagchi
- Department of Biochemistry and Biophysics, University of Kalyani, Nadia, India
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Rampioni G, Giallonardi G, D'Angelo F, Leoni L. A Coculture-Based Approach for Screening Campaigns Aimed at Identifying Novel Pseudomonas aeruginosa Quorum Sensing Inhibitors. Methods Mol Biol 2018; 1673:287-296. [PMID: 29130181 DOI: 10.1007/978-1-4939-7309-5_22] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Quorum sensing (QS) is recognized as a promising target for the identification of anti-virulence drugs hampering Pseudomonas aeruginosa adaptability to the host environment and pathogenicity. Consequently, a number of studies in the last decade focused on the identification of small molecules or proteins with anti-QS activity, mainly targeting the las QS system, which is based on N-3-oxododecanoyl-homoserine lactone (3OC12-HSL) as signal molecule. Different experimental approaches have been successfully used to identify QS blockers interfering with the activity/stability of the 3OC12-HSL receptor LasR, with the functionality of the 3OC12-HSL synthase LasI, or with the stability/bioavailability of the 3OC12-HSL signal molecule itself.Here we describe the use of a high-throughput screening system for the identification of novel las QS inhibitors based on the cocultivation of P. aeruginosa wild type and the P. aeruginosa-derived biosensor strain PA14-R3, in which light emission relies on the ability of the wild type strain to synthesize 3OC12-HSL and of the biosensor strain to perceive this signal molecule. With respect to other screening systems, this method has the advantage of being cost-effective and allowing the identification of compounds targeting, besides 3OC12-HSL reception, any cellular process critical for the functionality of the las QS system, including 3OC12-HSL synthesis and secretion.
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Affiliation(s)
- Giordano Rampioni
- Department of Science, University Roma Tre, Viale Guglielmo Marconi 446, 00146, Rome, Italy.
| | - Giulia Giallonardi
- Department of Science, University Roma Tre, Viale Guglielmo Marconi 446, 00146, Rome, Italy
| | - Francesca D'Angelo
- Department of Science, University Roma Tre, Viale Guglielmo Marconi 446, 00146, Rome, Italy
| | - Livia Leoni
- Department of Science, University Roma Tre, Viale Guglielmo Marconi 446, 00146, Rome, Italy
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Gene Duplication in Pseudomonas aeruginosa Improves Growth on Adenosine. J Bacteriol 2017; 199:JB.00261-17. [PMID: 28808129 DOI: 10.1128/jb.00261-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 08/05/2017] [Indexed: 11/20/2022] Open
Abstract
The laboratory strain of Pseudomonas aeruginosa, PAO1, activates genes for catabolism of adenosine using quorum sensing (QS). However, this strain is not well-adapted for growth on adenosine, with doubling times greater than 40 h. We previously showed that when PAO1 is grown on adenosine and casein, variants emerge that grow rapidly on adenosine. To understand the mechanism by which this adaptation occurs, we performed whole-genome sequencing of five isolates evolved for rapid growth on adenosine. All five genomes had a gene duplication-amplification (GDA) event covering several genes, including the quorum-regulated nucleoside hydrolase gene, nuh, and PA0148, encoding an adenine deaminase. In addition, two of the growth variants also exhibited a nuh promoter mutation. We recapitulated the rapid growth phenotype with a plasmid containing six genes common to all the GDA events. We also showed that nuh and PA0148, the two genes at either end of the common GDA, were sufficient to confer rapid growth on adenosine. Additionally, we demonstrated that the variant nuh promoter increased basal expression of nuh but maintained its QS regulation. Therefore, GDA in P. aeruginosa confers the ability to grow efficiently on adenosine while maintaining QS regulation of nucleoside catabolism.IMPORTANCEPseudomonas aeruginosa thrives in many habitats and is an opportunistic pathogen of humans. In these diverse environments, P. aeruginosa must adapt to use myriad potential carbon sources. P. aeruginosa PAO1 cannot grow efficiently on nucleosides, including adenosine; however, it can acquire this ability through genetic adaptation. We show that the mechanism of adaptation is by amplification of a specific region of the genome and that the amplification preserves the regulation of the adenosine catabolic pathway by quorum sensing. These results demonstrate an underexplored mechanism of adaptation by P. aeruginosa, with implications for phenotypes such as development of antibiotic resistance.
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Jagmann N, Bleicher V, Busche T, Kalinowski J, Philipp B. The guanidinobutyrase GbuA is essential for the alkylquinolone-regulated pyocyanin production during parasitic growth of Pseudomonas aeruginosa in co-culture with Aeromonas hydrophila. Environ Microbiol 2016; 18:3550-3564. [PMID: 27322205 DOI: 10.1111/1462-2920.13419] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 06/15/2016] [Indexed: 11/30/2022]
Abstract
The opportunistic pathogen Pseudomonas aeruginosa controls the production of virulence factors by quorum sensing (QS). Besides cell density, QS in P. aeruginosa is co-regulated by metabolic influences, especially nutrient limitation. Previously, a co-culture model system was established consisting of P. aeruginosa and the chitinolytic bacterium Aeromonas hydrophila, in which parasitic growth of P. aeruginosa is strictly dependent on the QS-controlled production of pyocyanin in response to nutrient limitation (Jagmann et al., ). In this study, the co-culture was employed to identify novel genes involved in the regulation of pyocyanin production. Via transposon mutagenesis, the gene gbuA encoding a guanidinobutyrase was identified, deletion of which led to a loss of pyocyanin production in co-cultures and to a reduced pyocyanin production in single cultures. Addition of the natural substrate of GbuA to the mutant strain enhanced the negative effect on pyocyanin production in single cultures. The gbuA mutant showed a reduced transcription of the pqsABCDE operon and could be complemented by PqsE overexpression and addition of alkylquinolone signal molecules. The strong effect of gbuA deletion on the QS-controlled pyocyanin production in co-cultures showed the value of this approach for the discovery of novel gene functions linking metabolism and QS in P. aeruginosa.
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Affiliation(s)
- Nina Jagmann
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität (WWU) Münster, Corrensstr. 3, Münster, 48149, Germany
| | - Vera Bleicher
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität (WWU) Münster, Corrensstr. 3, Münster, 48149, Germany
| | - Tobias Busche
- Center for Biotechnology (CeBiTec), Universität Bielefeld, Universitätsstr. 25, Bielefeld, 33615, Germany
| | - Jörn Kalinowski
- Center for Biotechnology (CeBiTec), Universität Bielefeld, Universitätsstr. 25, Bielefeld, 33615, Germany
| | - Bodo Philipp
- Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität (WWU) Münster, Corrensstr. 3, Münster, 48149, Germany.
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Lixa C, Marques AF, Cortines JR, Neves BC, Oliveira DM, Anobom CD, Lima LMT, Pinheiro AS. Refolding, purification, and preliminary structural characterization of the DNA-binding domain of the quorum sensing receptor RhlR from Pseudomonas aeruginosa. Protein Expr Purif 2016; 121:31-40. [DOI: 10.1016/j.pep.2016.01.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 12/18/2015] [Accepted: 01/08/2016] [Indexed: 12/22/2022]
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Grant PK, Dalchau N, Brown JR, Federici F, Rudge TJ, Yordanov B, Patange O, Phillips A, Haseloff J. Orthogonal intercellular signaling for programmed spatial behavior. Mol Syst Biol 2016; 12:849. [PMID: 26814193 PMCID: PMC4731010 DOI: 10.15252/msb.20156590] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Revised: 11/19/2015] [Accepted: 11/23/2015] [Indexed: 12/31/2022] Open
Abstract
Bidirectional intercellular signaling is an essential feature of multicellular organisms, and the engineering of complex biological systems will require multiple pathways for intercellular signaling with minimal crosstalk. Natural quorum-sensing systems provide components for cell communication, but their use is often constrained by signal crosstalk. We have established new orthogonal systems for cell-cell communication using acyl homoserine lactone signaling systems. Quantitative measurements in contexts of differing receiver protein expression allowed us to separate different types of crosstalk between 3-oxo-C6- and 3-oxo-C12-homoserine lactones, cognate receiver proteins, and DNA promoters. Mutating promoter sequences minimized interactions with heterologous receiver proteins. We used experimental data to parameterize a computational model for signal crosstalk and to estimate the effect of receiver protein levels on signal crosstalk. We used this model to predict optimal expression levels for receiver proteins, to create an effective two-channel cell communication device. Establishment of a novel spatial assay allowed measurement of interactions between geometrically constrained cell populations via these diffusible signals. We built relay devices capable of long-range signal propagation mediated by cycles of signal induction, communication and response by discrete cell populations. This work demonstrates the ability to systematically reduce crosstalk within intercellular signaling systems and to use these systems to engineer complex spatiotemporal patterning in cell populations.
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Affiliation(s)
- Paul K Grant
- Department of Plant Sciences, University of Cambridge, Cambridge, UK Computational Science Laboratory, Microsoft Research, Cambridge, UK
| | - Neil Dalchau
- Computational Science Laboratory, Microsoft Research, Cambridge, UK
| | - James R Brown
- Department of Plant Sciences, University of Cambridge, Cambridge, UK Computational Science Laboratory, Microsoft Research, Cambridge, UK
| | - Fernan Federici
- Department of Plant Sciences, University of Cambridge, Cambridge, UK Departamento de Genética Molecular y Microbiologia, Facultad de Cs. Biológicas, Universidad Católica de Chile, Santiago, Chile
| | - Timothy J Rudge
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Boyan Yordanov
- Computational Science Laboratory, Microsoft Research, Cambridge, UK
| | - Om Patange
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
| | - Andrew Phillips
- Computational Science Laboratory, Microsoft Research, Cambridge, UK
| | - Jim Haseloff
- Department of Plant Sciences, University of Cambridge, Cambridge, UK
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Lovaglio R, Silva V, Ferreira H, Hausmann R, Contiero J. Rhamnolipids know-how: Looking for strategies for its industrial dissemination. Biotechnol Adv 2015; 33:1715-26. [DOI: 10.1016/j.biotechadv.2015.09.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 09/02/2015] [Accepted: 09/06/2015] [Indexed: 11/29/2022]
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González-Valdez A, Servín-González L, Juárez K, Hernandez-Aligio A, Soberón-Chávez G. The effect of specific rhlA-las-box mutations on DNA binding and gene activation by Pseudomonas aeruginosa quorum-sensing transcriptional regulators RhlR and LasR. FEMS Microbiol Lett 2015; 356:217-25. [PMID: 24935161 DOI: 10.1111/1574-6968.12505] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Revised: 06/05/2014] [Accepted: 06/07/2014] [Indexed: 01/22/2023] Open
Abstract
Pseudomonas aeruginosa is a free-living bacterium and an important opportunistic pathogen. The genes coding for virulence-associated traits are regulated at the level of transcription by the quorum-sensing response. In this response, the regulator LasR coupled with the autoinducer 3-oxo-dodecanoyl homoserine lactone (3O-C12-HSL) activates transcription of genes for several virulence factors. LasR/3O-C12-HSL also activates transcription of rhlR, the gene coding for the transcriptional regulator RhlR, and of rhlI that encodes the synthase that produces the autoinducer butanoyl-homoserine lactone (C4-HSL) that interacts with RhlR. Genes activated by RhlR/C4-HSL include those involved in rhamnolipids production (like the rhlAB operon) and lecA, coding for PA-I lectin. The molecular basis of LasR/3O-C12-HSL- and RhlR/C4-HSLDNA-binding specificity (at the so-called las-boxes) has not been clearly determined, and the aim of this work was to contribute to its understanding. Therefore, we analyzed the interaction of LasR and RhlR to variants of the rhlA-las-box that were constructed based on the comparison of this las-box to the las-box of lecA. We conclude that LasR and RhlR DNA-binding specificity is a complex multifactorial phenomenon in which both positive and negative effects are involved and that binding of these proteins does not necessarily result in gene activation.
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Affiliation(s)
- Abigail González-Valdez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México, México
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CysB Negatively Affects the Transcription of pqsR and Pseudomonas Quinolone Signal Production in Pseudomonas aeruginosa. J Bacteriol 2015; 197:1988-2002. [PMID: 25845844 DOI: 10.1128/jb.00246-15] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Accepted: 03/27/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Pseudomonas aeruginosa is a Gram-negative bacterium that is ubiquitous in the environment, and it is an opportunistic pathogen that can infect a variety of hosts, including humans. During the process of infection, P. aeruginosa coordinates the expression of numerous virulence factors through the production of multiple cell-to-cell signaling molecules. The production of these signaling molecules is linked through a regulatory network, with the signal N-(3-oxododecanoyl) homoserine lactone and its receptor LasR controlling the induction of a second acyl-homoserine lactone signal and the Pseudomonas quinolone signal (PQS). LasR-mediated control of PQS occurs partly by activating the transcription of pqsR, a gene that encodes the PQS receptor and is necessary for PQS production. We show that LasR interacts with a single binding site in the pqsR promoter region and that it does not influence the transcription of the divergently transcribed gene, nadA. Using DNA affinity chromatography, we identified additional proteins that interact with the pqsR-nadA intergenic region. These include the H-NS family members MvaT and MvaU, and CysB, a transcriptional regulator that controls sulfur uptake and cysteine biosynthesis. We show that CysB interacts with the pqsR promoter and that CysB represses pqsR transcription and PQS production. Additionally, we provide evidence that CysB can interfere with the activation of pqsR transcription by LasR. However, as seen with other CysB-regulated genes, pqsR expression was not differentially regulated in response to cysteine levels. These findings demonstrate a novel role for CysB in influencing cell-to-cell signal production by P. aeruginosa. IMPORTANCE The production of PQS and other 4-hydroxy-2-alkylquinolone (HAQs) compounds is a key component of the P. aeruginosa cell-to-cell signaling network, impacts multiple physiological functions, and is required for virulence. PqsR directly regulates the genes necessary for HAQ production, but little is known about the regulation of pqsR. We identified CysB as a novel regulator of pqsR and PQS production, but, unlike other CysB-controlled genes, it does not appear to regulate pqsR in response to cysteine. This implies that CysB functions as both a cysteine-responsive and cysteine-unresponsive regulator in P. aeruginosa.
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Subramoni S, Florez Salcedo DV, Suarez-Moreno ZR. A bioinformatic survey of distribution, conservation, and probable functions of LuxR solo regulators in bacteria. Front Cell Infect Microbiol 2015; 5:16. [PMID: 25759807 PMCID: PMC4338825 DOI: 10.3389/fcimb.2015.00016] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2014] [Accepted: 02/02/2015] [Indexed: 12/25/2022] Open
Abstract
LuxR solo transcriptional regulators contain both an autoinducer binding domain (ABD; N-terminal) and a DNA binding Helix-Turn-Helix domain (HTH; C-terminal), but are not associated with a cognate N-acyl homoserine lactone (AHL) synthase coding gene in the same genome. Although a few LuxR solos have been characterized, their distributions as well as their role in bacterial signal perception and other processes are poorly understood. In this study we have carried out a systematic survey of distribution of all ABD containing LuxR transcriptional regulators (QS domain LuxRs) available in the InterPro database (IPR005143), and identified those lacking a cognate AHL synthase. These LuxR solos were then analyzed regarding their taxonomical distribution, predicted functions of neighboring genes and the presence of complete AHL-QS systems in the genomes that carry them. Our analyses reveal the presence of one or multiple predicted LuxR solos in many proteobacterial genomes carrying QS domain LuxRs, some of them harboring genes for one or more AHL-QS circuits. The presence of LuxR solos in bacteria occupying diverse environments suggests potential ecological functions for these proteins beyond AHL and interkingdom signaling. Based on gene context and the conservation levels of invariant amino acids of ABD, we have classified LuxR solos into functionally meaningful groups or putative orthologs. Surprisingly, putative LuxR solos were also found in a few non-proteobacterial genomes which are not known to carry AHL-QS systems. Multiple predicted LuxR solos in the same genome appeared to have different levels of conservation of invariant amino acid residues of ABD questioning their binding to AHLs. In summary, this study provides a detailed overview of distribution of LuxR solos and their probable roles in bacteria with genome sequence information.
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Affiliation(s)
- Sujatha Subramoni
- Grupo de Bioprospección, Facultad de Ingeniería, Universidad de La Sabana, Campus del Puente del Común Chía, Colombia
| | | | - Zulma R Suarez-Moreno
- Grupo de Bioprospección, Facultad de Ingeniería, Universidad de La Sabana, Campus del Puente del Común Chía, Colombia
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The hierarchy quorum sensing network in Pseudomonas aeruginosa. Protein Cell 2014; 6:26-41. [PMID: 25249263 PMCID: PMC4286720 DOI: 10.1007/s13238-014-0100-x] [Citation(s) in RCA: 750] [Impact Index Per Article: 75.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 08/28/2014] [Indexed: 12/13/2022] Open
Abstract
Pseudomonas aeruginosa causes severe and persistent infections in immune compromised individuals and cystic fibrosis sufferers. The infection is hard to eradicate as P. aeruginosa has developed strong resistance to most conventional antibiotics. The problem is further compounded by the ability of the pathogen to form biofilm matrix, which provides bacterial cells a protected environment withstanding various stresses including antibiotics. Quorum sensing (QS), a cell density-based intercellular communication system, which plays a key role in regulation of the bacterial virulence and biofilm formation, could be a promising target for developing new strategies against P. aeruginosa infection. The QS network of P. aeruginosa is organized in a multi-layered hierarchy consisting of at least four interconnected signaling mechanisms. Evidence is accumulating that the QS regulatory network not only responds to bacterial population changes but also could react to environmental stress cues. This plasticity should be taken into consideration during exploration and development of anti-QS therapeutics.
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Bazire A, Dufour A. The Pseudomonas aeruginosa rhlG and rhlAB genes are inversely regulated and RhlG is not required for rhamnolipid synthesis. BMC Microbiol 2014; 14:160. [PMID: 24943492 PMCID: PMC4074388 DOI: 10.1186/1471-2180-14-160] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 06/12/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Pseudomonas aeruginosa produces rhamnolipid biosurfactants involved in numerous phenomena including virulence. The transcriptional study of the rhlAB operon encoding two key enzymes for rhamnolipid synthesis led to the discovery of the quorum sensing system RhlRI. The latter positively controls the transcription of rhlAB, as well as of rhlC, which is required for di-rhamnolipid synthesis. The rhlG gene encodes an NADPH-dependent β-ketoacyl reductase. Although it was reported to be required for the biosynthesis of the fatty acid part of rhamnolipids, its function in rhamnolipid synthesis was later questioned. The rhlG transcription and its role in rhamnolipid production were investigated here. RESULTS Using 5'-RACE PCR, a luxCDABE-based transcriptional fusion, and quantitative reverse transcription-PCR, we confirmed two previously identified σ70- and σ54-dependent promoters and we identified a third promoter recognized by the extra-cytoplasmic function sigma factor AlgU. rhlG was inversely regulated compared to rhlAB and rhlC: the rhlG transcription was down-regulated in response to N-butyryl-l-homoserine lactone, the communication molecule of the RhlRI system, and was induced by hyperosmotic stress in an AlgU-dependent manner. Consistently with this transcriptional pattern, the single or double deletions of rhlG and PA3388, which forms an operon with rhlG, did not dramatically impair rhamnolipid synthesis. CONCLUSION This first detailed study of rhlG transcription reveals a complex regulation involving three sigma factors and N-butyryl-l-homoserine lactone. We furthermore present evidences that RhlG does not play a key role in rhamnolipid synthesis.
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Affiliation(s)
- Alexis Bazire
- Université de Bretagne-Sud, EA 3884, LBCM, IUEM, F-56100 Lorient, France.
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41
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Scott-Phillips TC, Gurney J, Ivens A, Diggle SP, Popat R. Combinatorial communication in bacteria: implications for the origins of linguistic generativity. PLoS One 2014; 9:e95929. [PMID: 24759740 PMCID: PMC3997515 DOI: 10.1371/journal.pone.0095929] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Accepted: 04/02/2014] [Indexed: 11/29/2022] Open
Abstract
Combinatorial communication, in which two signals are used together to achieve an effect that is different to the sum of the effects of the component parts, is apparently rare in nature: it is ubiquitous in human language, appears to exist in a simple form in some non-human primates, but has not been demonstrated in other species. This observed distribution has led to the pair of related suggestions, that (i) these differences in the complexity of observed communication systems reflect cognitive differences between species; and (ii) that the combinations we see in non-human primates may be evolutionary pre-cursors of human language. Here we replicate the landmark experiments on combinatorial communication in non-human primates, but in an entirely different species, unrelated to humans, and with no higher cognition: the bacterium Pseudomonas aeruginosa. Using the same general methods as the primate studies, we find the same general pattern of results: the effect of the combined signal differs from the composite effect of the two individual signals. This suggests that advanced cognitive abilities and large brains do not necessarily explain why some species have combinatorial communication systems and others do not. We thus argue that it is premature to conclude that the systems observed in non-human primates are evolutionarily related to language. Our results illustrate the value of an extremely broad approach to comparative research.
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Affiliation(s)
| | - James Gurney
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Alasdair Ivens
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Edinburgh, United Kingdom
| | - Stephen P. Diggle
- School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - Roman Popat
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Edinburgh, United Kingdom
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Panijel M, Chalupowicz L, Sessa G, Manulis-Sasson S, Barash I. Global regulatory networks control the hrp regulon of the gall-forming bacterium Pantoea agglomerans pv. gypsophilae. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2013; 26:1031-1043. [PMID: 23745675 DOI: 10.1094/mpmi-04-13-0097-r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Gall formation by Pantoea agglomerans pv. gypsophilae is dependent on the hypersensitive response and pathogenicity (hrp) system. Previous studies demonstrated that PagR and PagI, regulators of the quorum-sensing system, induce expression of the hrp regulatory cascade (i.e., hrpXY, hrpS, and hrpL) that activates the HrpL regulon. Here, we isolated the genes of the Gac/Rsm global regulatory pathway (i.e., gacS, gacA, rsmB, and csrD) and of the post-transcriptional regulator rsmA. Our results demonstrate that PagR and PagI also upregulate expression of the Gac/Rsm pathway. PagR acts as a transcriptional activator of each of the hrp regulatory genes and gacA in a N-butanoyl-L-homoserine lactone-dependent manner as shown by gel shift experiments. Mutants of the Gac/Rsm genes or overexpression of rsmA significantly reduced Pantoea agglomerans virulence and colonization of gypsophila. Overexpression of rsmB sRNA abolished gall formation, colonization, and hypersensitive reaction on nonhost plants and prevented transcription of the hrp regulatory cascade, indicating a lack of functional type III secretion system. Expression of rsmB sRNA in the background of the csrD null mutant suggests that CsrD may act as a safeguard for preventing excessive production of rsmB sRNA. Results presented indicate that the hrp regulatory cascade is controlled directly by PagR and indirectly by RsmA, whereas deficiency in RsmA activity is epistatic to PagR induction.
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Affiliation(s)
- Mary Panijel
- Department of Molecular Biology and Ecology of Plants, Tel-Aviv University, Tel-Aviv, Israel
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Banderas A, Guiliani N. Bioinformatic prediction of gene functions regulated by quorum sensing in the bioleaching bacterium Acidithiobacillus ferrooxidans. Int J Mol Sci 2013; 14:16901-16. [PMID: 23959118 PMCID: PMC3759942 DOI: 10.3390/ijms140816901] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Revised: 07/18/2013] [Accepted: 07/22/2013] [Indexed: 12/14/2022] Open
Abstract
The biomining bacterium Acidithiobacillus ferrooxidans oxidizes sulfide ores and promotes metal solubilization. The efficiency of this process depends on the attachment of cells to surfaces, a process regulated by quorum sensing (QS) cell-to-cell signalling in many Gram-negative bacteria. At. ferrooxidans has a functional QS system and the presence of AHLs enhances its attachment to pyrite. However, direct targets of the QS transcription factor AfeR remain unknown. In this study, a bioinformatic approach was used to infer possible AfeR direct targets based on the particular palindromic features of the AfeR binding site. A set of Hidden Markov Models designed to maintain palindromic regions and vary non-palindromic regions was used to screen for putative binding sites. By annotating the context of each predicted binding site (PBS), we classified them according to their positional coherence relative to other putative genomic structures such as start codons, RNA polymerase promoter elements and intergenic regions. We further used the Multiple EM for Motif Elicitation algorithm (MEME) to further filter out low homology PBSs. In summary, 75 target-genes were identified, 34 of which have a higher confidence level. Among the identified genes, we found afeR itself, zwf, genes encoding glycosyltransferase activities, metallo-beta lactamases, and active transport-related proteins. Glycosyltransferases and Zwf (Glucose 6-phosphate-1-dehydrogenase) might be directly involved in polysaccharide biosynthesis and attachment to minerals by At. ferrooxidans cells during the bioleaching process.
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Affiliation(s)
- Alvaro Banderas
- Authors to whom correspondence should be addressed; E-Mails: (A.B.); (N.G.); Tel.: +49-06221-546846 (A.B.); +56-2-2978-7241 (N.G.)
| | - Nicolas Guiliani
- Laboratory of Bacterial Communication, Department of Biology, Faculty of Sciences, University of Chile, Santiago 780-0024, Chile
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Matcher GF, Jiwaji M, de la Mare JA, Dorrington RA. Complex pathways for regulation of pyrimidine metabolism by carbon catabolite repression and quorum sensing in Pseudomonas putida RU-KM3S. Appl Microbiol Biotechnol 2013; 97:5993-6007. [DOI: 10.1007/s00253-013-4862-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2013] [Accepted: 03/13/2013] [Indexed: 11/28/2022]
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45
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Yong YC, Zhong JJ. Regulation of aromatics biodegradation by rhl quorum sensing system through induction of catechol meta-cleavage pathway. BIORESOURCE TECHNOLOGY 2013; 136:761-765. [PMID: 23582222 DOI: 10.1016/j.biortech.2013.03.134] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Revised: 03/17/2013] [Accepted: 03/18/2013] [Indexed: 06/02/2023]
Abstract
The mechanism for quorum sensing (QS) regulation on aromatics degradation was investigated. Deletion of rhl QS system resulted in a significant decrease in aromatics biodegradation as well as the activity of catechol 2,3-dioxygenase (C23O, key enzyme for catechol meta-cleavage pathway) in Pseudomonas aeruginosa CGMCC1.860. Interestingly, this repression could be relieved by N-butyryl homoserine lactone (the signaling molecule of rhl QS system) addition. In accordance, the transcription level of nahH (the gene encoding C23O) and nahR (transcriptional activator) also responded to rhl perturbation in a similar way. The results indicated that rhl QS system positively controlled the catechol meta-cleavage pathway, and hence improved aromatics biodegradation. It suggested manipulation of QS system could be a promising strategy to tune the catechol cleavage pathway and to control aromatics biodegradation.
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Affiliation(s)
- Yang-Chun Yong
- Biofuels Institute, School of the Environment, Jiangsu University, 301 Xuefu Road, Zhenjiang 212013, Jiangsu Province, China
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Redundant phenazine operons in Pseudomonas aeruginosa exhibit environment-dependent expression and differential roles in pathogenicity. Proc Natl Acad Sci U S A 2012; 109:19420-5. [PMID: 23129634 DOI: 10.1073/pnas.1213901109] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Evolutionary biologists have postulated that several fitness advantages may be conferred by the maintenance of duplicate genes, including environmental adaptation resulting from differential regulation. We examined the expression and physiological contributions of two redundant operons in the adaptable bacterium Pseudomonas aeruginosa PA14. These operons, phzA1-G1 (phz1) and phzA2-G2 (phz2), encode nearly identical sets of proteins that catalyze the synthesis of phenazine-1-carboxylic acid, the precursor for several phenazine derivatives. Phenazines perform diverse roles in P. aeruginosa physiology and act as virulence factors during opportunistic infections of plant and animal hosts. Although reports have indicated that phz1 is regulated by the Pseudomonas quinolone signal, factors controlling phz2 expression have not been identified, and the relative contributions of these redundant operons to phenazine biosynthesis have not been evaluated. We found that in liquid cultures, phz1 was expressed at higher levels than phz2, although phz2 showed a greater contribution to phenazine production. In colony biofilms, phz2 was expressed at high levels, whereas phz1 expression was not detectable, and phz2 was responsible for virtually all phenazine production. Analysis of mutants defective in quinolone signal synthesis revealed a critical role for 4-hydroxy-2-heptylquinoline in phz2 induction. Finally, deletion of phz2, but not of phz1, decreased lung colonization in a murine model of infection. These results suggest that differential regulation of the redundant phz operons allows P. aeruginosa to adapt to diverse environments.
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Leung MM, Brimacombe CA, Spiegelman GB, Beatty JT. The GtaR protein negatively regulates transcription of the gtaRI operon and modulates gene transfer agent (RcGTA) expression in Rhodobacter capsulatus. Mol Microbiol 2012; 83:759-74. [PMID: 22211723 PMCID: PMC3641048 DOI: 10.1111/j.1365-2958.2011.07963.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The gtaI gene of Rhodobacter capsulatus encodes an N-acyl-homoserine lactone (acyl-HSL) synthase. Immediately 5' of the gtaI gene is ORF rcc00328 that encodes a potential acyl-HSL receptor protein. A combination of genetic and biochemical approaches showed that rcc00328 (renamed gtaR) modulates the production of a genetic exchange element called the gene transfer agent (RcGTA), and regulates the transcription of gtaI. Although gtaI mutants exhibited decreased levels of RcGTA production, mutagenesis of gtaR did not, whereas a gtaR/gtaI double mutant produced wild-type levels of RcGTA. Because mutagenesis of gtaR suppressed the effect of the gtaI mutation, we suggest that the GtaR protein is a negative transcriptional regulator of RcGTA gene expression. We discovered that the gtaR and gtaI genes are co-transcribed, and also negatively regulated by the GtaR protein in the absence of acyl-HSL. A His-tagged GtaR protein was purified, and DNA-binding experiments revealed a binding site in the promoter region of the gtaRI operon. This GtaR protein did not bind to the RcGTA promoter region, and therefore modulation of RcGTA production appears to require at least one additional factor. We found that RcGTA production was stimulated by spent media from other species, and identified exogenous acyl-HSLs that induce RcGTA.
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Affiliation(s)
| | | | - G. B. Spiegelman
- Department of Microbiology and Immunology, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
| | - J. Thomas Beatty
- Department of Microbiology and Immunology, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada
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48
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Aguirre-Ramírez M, Medina G, González-Valdez A, Grosso-Becerra V, Soberón-Chávez G. The Pseudomonas aeruginosa rmlBDAC operon, encoding dTDP-L-rhamnose biosynthetic enzymes, is regulated by the quorum-sensing transcriptional regulator RhlR and the alternative sigma factor σS. MICROBIOLOGY-SGM 2012; 158:908-916. [PMID: 22262098 DOI: 10.1099/mic.0.054726-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Pseudomonas aeruginosa produces as biosurfactants rhamnolipids, containing one (mono-rhamnolipid) or two (di-rhamnolipid) l-rhamnose molecules. The rhamnosyltransferase RhlB catalyses the synthesis of mono-rhamnolipid using as precursors dTDP-l-rhamnose and 3-(3-hydroxyalkanoyloxy)alkanoic acids (HAAs) produced by RhlA, while the rhamnosyltransferase RhlC synthesizes di-rhamnolipid using mono-rhamnolipid and dTDP-l-rhamnose as substrates. The Las and Rhl quorum-sensing systems coordinately regulate the production of these surfactants, as well as that of other exoproducts involved in bacterial virulence, at the transcriptional level in a cell density-dependent manner. In this work we study the transcriptional regulation of the rmlBDAC operon, encoding the enzymes involved in the production of dTDP-l-rhamnose, the substrate of both rhamnosyltransferases, RhlB and RhlC, and also a component of P. aeruginosa lipopolysaccharide. Here we show that the rmlBDAC operon possesses three promoters. One of these transcriptional start sites (P2) is responsible for most of its expression and is dependent on the stationary phase sigma factor σ(S) and on RhlR/C(4)-HSL through its binding to an atypical 'las box'.
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Affiliation(s)
- Marisela Aguirre-Ramírez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, México D. F., México
| | - Gerardo Medina
- Universidad Autónoma de Baja California, Mexicali, BC, México
| | - Abigail González-Valdez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, México D. F., México
| | - Victoria Grosso-Becerra
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, México D. F., México
| | - Gloria Soberón-Chávez
- Departamento de Biología Molecular y Biotecnología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México (UNAM), Ciudad Universitaria, México D. F., México
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Ha C, Park SJ, Im SJ, Park SJ, Lee JH. Interspecies signaling through QscR, a quorum receptor of Pseudomonas aeruginosa. Mol Cells 2012; 33:53-9. [PMID: 22228182 PMCID: PMC3887745 DOI: 10.1007/s10059-012-2208-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Revised: 10/21/2011] [Accepted: 10/24/2011] [Indexed: 10/14/2022] Open
Abstract
The QS machinery of Pseudomonas aeruginosa, an opportunistic human pathogen, consists of three acyl-homoserine lactone (acyl-HSL) signaling systems, LasR-I, RhlR-I, and QscR. QscR, known as an orphan receptor and a repressor of other QS systems, operates its own regulon using N-3-oxododecanoyl HSL (3OC12), which is synthesized by LasI, as its signal. In this study, we addressed the role of QscR in interspecies communication. We found that QscR auto-activates its own transcription in the presence of 3OC12. In a single population of P. aeruginosa, where 3OC12 is the sole signal available for QscR, the QscR regulon is activated by 3OC12 produced by the LasI-R system. However, the broad signal specificity of QscR allowed it to respond to a non-P. aeruginosa signal, such as N-decanoyl HSL (C10) and N-3-hydroxydecanoyl HSL (3OHC10), which preferentially activated QscR to LasR. The signal extracts from Pseudomonas fluorescens and Burkholeria vietnamiensis also preferentially activated QscR. These non-P. aeruginosa signals activated QscR more strongly than 3OC12, the authentic P. aeruginosa signal. Since a variety of acyl-HSLs are produced in the multi-species habitat of nature, our study provides a clue for the particular situation that allows QscR to secede from the conventional QS cascade in mixed microbial community.
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Affiliation(s)
| | | | - Su-Jin Im
- Department of Pharmacy, College of Pharmacy, Pusan National University, Busan 609-735,
Korea
| | - Su-Jin Park
- Department of Pharmacy, College of Pharmacy, Pusan National University, Busan 609-735,
Korea
| | - Joon-Hee Lee
- Department of Pharmacy, College of Pharmacy, Pusan National University, Busan 609-735,
Korea
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50
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Venturi V, Rampioni G, Pongor S, Leoni L. The virtue of temperance: built-in negative regulators of quorum sensing in Pseudomonas. Mol Microbiol 2011; 82:1060-70. [PMID: 22060261 DOI: 10.1111/j.1365-2958.2011.07890.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Many bacteria are now believed to produce small signal molecules in order to communicate in a process called quorum sensing (QS), which mediates cooperative traits and a co-ordinated behaviour. Pseudomonads have been extensively studied for their QS response highlighting that it plays a major role in determining their lifestyle. The main QS signal molecules produced by Pseudomonas belong to the family of N-acyl-homoserine lactones (AHLs); these are synthesized by a LuxI-family synthase and sensed by a LuxR-family regulator. Most often in Pseudomonas, repressor genes intergenically located between luxI and luxR form an integral part of QS system. Recent studies have highlighted an important role of these repressors (called RsaL and RsaM) in containing the QS response within cost-effective levels; this is central for pseudomonads as they have very versatile genomes allowing them to live in constantly changing and highly dynamic environments. This review focuses on the role played by RsaL and RsaM repressors and discusses the important implications of this control of the QS response.
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Affiliation(s)
- Vittorio Venturi
- International Centre for Genetic Engineering and Biotechnology, Padriciano, 99, 34012 Trieste, Italy.
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