201
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Liaqat I, Bachmann RT, Edyvean RGJ. Type 2 quorum sensing monitoring, inhibition and biofilm formation in marine microrganisms. Curr Microbiol 2013; 68:342-51. [PMID: 24166155 DOI: 10.1007/s00284-013-0484-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 09/11/2013] [Indexed: 12/11/2022]
Abstract
The quorum sensing (QS) dependent behaviour of micro-organisms, in particular expression of virulence genes, biofilm formation and dispersal, have provided impetus for investigating practical approaches to interfere with microbial QS. This study tests Halomonas pacifica and Marinobacter hydrocarbonoclasticus, two halophilic marine micro-organism, for their AI-2 dependent QS signalling and the effect of two well-known quorum-sensing inhibitors (QSIs), patulin and penicillic acid, on biofilm formation. We report, for the first time, the successful amplification of a putative luxS gene in H. pacifica using degenerated primers and AI-2 dependent QS as well as inhibition using QSIs. Penicillic acid had a strong inhibitory effect on AI-2 induction of H. pacifica at non-growth inhibitory concentrations, while patulin has an adverse effect only at the highest concentration (25 μM). QSIs effect on biofilm forming capability was isolate specific, with maximum inhibition at 25 μM of patulin in H. pacifica. In M. hydrocarbonoclasticus, no adverse effects were noted at any tested concentration of either QSIs. Detection of bioluminescence and the presence of a putative luxS gene provide biochemical and genetic evidence for the production of a signalling molecule(s) which is the essential first step in characterizing H. pacifica QS. This study highlights the importance of AI-2 dependent QS in a marine setting, not previously reported. It further suggests that QSI compounds must be selected in the specific system in which they are to function, and they cannot easily be transferred from one QS system to another.
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Affiliation(s)
- Iram Liaqat
- Department of Zoology, Government College University, Lahore, Pakistan,
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202
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Raut N, Pasini P, Daunert S. Deciphering Bacterial Universal Language by Detecting the Quorum Sensing Signal, Autoinducer-2, with a Whole-Cell Sensing System. Anal Chem 2013; 85:9604-9. [DOI: 10.1021/ac401776k] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Nilesh Raut
- Department
of Chemistry, University of Kentucky, Lexington, Kentucky 40506, United States
| | - Patrizia Pasini
- Department
of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, Florida 33136, United States
| | - Sylvia Daunert
- Department
of Biochemistry and Molecular Biology, Miller School of Medicine, University of Miami, Miami, Florida 33136, United States
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203
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Elgaml A, Higaki K, Miyoshi SI. Effects of temperature, growth phase and luxO-disruption on regulation systems of toxin production in Vibrio vulnificus strain L-180, a human clinical isolate. World J Microbiol Biotechnol 2013; 30:681-91. [DOI: 10.1007/s11274-013-1501-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Accepted: 09/18/2013] [Indexed: 12/19/2022]
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204
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Substrate specificity and function of the pheromone receptor AinR in Vibrio fischeri ES114. J Bacteriol 2013; 195:5223-32. [PMID: 24056099 DOI: 10.1128/jb.00913-13] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Two distinct but interrelated pheromone-signaling systems, LuxI/LuxR and AinS/AinR, positively control bioluminescence in Vibrio fischeri. Although each system generates an acyl-homoserine lactone (AHL) signal, the protein sequences of LuxI/LuxR and AinS/AinR are unrelated. AinS and LuxI generate the pheromones N-octanoyl-AHL (C8-AHL) and N-3-oxo-hexanoyl-AHL (3OC6-AHL), respectively. LuxR is a transcriptional activator that responds to 3OC6-AHL, and to a lesser extent to C8-AHL. AinR is hypothesized to respond to C8-AHL and, based on homology to Vibrio harveyi LuxN, to mediate the repression of a Qrr regulatory RNA. However, a ΔainR mutation decreased luminescence, which was not predicted based on V. harveyi LuxN, raising the possibility of a distinct regulatory mechanism for AinR. Here we show that ainR can complement a luxN mutant, suggesting functional similarity. Moreover, in V. fischeri, we observed ainR-dependent repression of a Pqrr-lacZ transcriptional reporter in the presence of C8-AHL, consistent with its hypothesized regulatory role. The system appears quite sensitive, with a half-maximal effect on a Pqrr reporter at 140 pM C8-AHL. Several other AHLs with substituted and unsubstituted acyl chains between 6 and 10 carbons also displayed an AinR-dependent effect on Pqrr-lacZ; however, AHLs with acyl chains of four carbons or 12 or more carbons lacked activity. Interestingly, 3OC6-AHL also affected expression from the qrr promoter, but this effect was largely luxR dependent, indicating a previously unknown connection between these systems. Finally, we propose a preliminary explanation for the unexpected luminescence phenotype of the ΔainR mutant.
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205
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Kim T, Spiegel DA. Serendipitous discovery of two highly selective inhibitors of bacterial luciferase. Tetrahedron 2013. [DOI: 10.1016/j.tet.2013.05.086] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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206
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A nitric oxide-responsive quorum sensing circuit in Vibrio harveyi regulates flagella production and biofilm formation. Int J Mol Sci 2013; 14:16473-84. [PMID: 23965964 PMCID: PMC3759921 DOI: 10.3390/ijms140816473] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Accepted: 07/26/2013] [Indexed: 01/01/2023] Open
Abstract
Cell signaling plays an important role in the survival of bacterial colonies. They use small molecules to coordinate gene expression in a cell density dependent manner. This process, known as quorum sensing, helps bacteria regulate diverse functions such as bioluminescence, biofilm formation and virulence. In Vibrio harveyi, a bioluminescent marine bacterium, four parallel quorum-sensing systems have been identified to regulate light production. We have previously reported that nitric oxide (NO), through the H-NOX/HqsK quorum sensing pathway contributes to light production in V. harveyi through the LuxU/LuxO/LuxR quorum sensing pathway. In this study, we show that nitric oxide (NO) also regulates flagellar production and enhances biofilm formation. Our data suggest that V. harveyi is capable of switching between lifestyles to be able to adapt to changes in the environment.
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207
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Affiliation(s)
- Mohammad Asif
- Department of Pharmacy, GRD (PG) Institute of Management and Technology, Dehradun, Uttarakhand, India
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208
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Wright CJ, Burns LH, Jack AA, Back CR, Dutton LC, Nobbs AH, Lamont RJ, Jenkinson HF. Microbial interactions in building of communities. Mol Oral Microbiol 2013; 28:83-101. [PMID: 23253299 PMCID: PMC3600090 DOI: 10.1111/omi.12012] [Citation(s) in RCA: 130] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/31/2012] [Indexed: 12/31/2022]
Abstract
Establishment of a community is considered to be essential for microbial growth and survival in the human oral cavity. Biofilm communities have increased resilience to physical forces, antimicrobial agents and nutritional variations. Specific cell-to-cell adherence processes, mediated by adhesin-receptor pairings on respective microbial surfaces, are able to direct community development. These interactions co-localize species in mutually beneficial relationships, such as streptococci, veillonellae, Porphyromonas gingivalis and Candida albicans. In transition from the planktonic mode of growth to a biofilm community, microorganisms undergo major transcriptional and proteomic changes. These occur in response to sensing of diffusible signals, such as autoinducer molecules, and to contact with host tissues or other microbial cells. Underpinning many of these processes are intracellular phosphorylation events that regulate a large number of microbial interactions relevant to community formation and development.
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Affiliation(s)
- Christopher J. Wright
- Department of Oral Health and Systemic Disease, University of Louisville, 570 South Preston Street, Louisville, Kentucky, 40202, USA
| | - Logan H. Burns
- Department of Oral Health and Systemic Disease, University of Louisville, 570 South Preston Street, Louisville, Kentucky, 40202, USA
| | - Alison A. Jack
- School of Oral and Dental Sciences, University of Bristol, Lower Maudlin Street, Bristol BS12LY, UK
| | - Catherine R. Back
- School of Oral and Dental Sciences, University of Bristol, Lower Maudlin Street, Bristol BS12LY, UK
| | - Lindsay C. Dutton
- School of Oral and Dental Sciences, University of Bristol, Lower Maudlin Street, Bristol BS12LY, UK
| | - Angela H. Nobbs
- School of Oral and Dental Sciences, University of Bristol, Lower Maudlin Street, Bristol BS12LY, UK
| | - Richard J. Lamont
- Department of Oral Health and Systemic Disease, University of Louisville, 570 South Preston Street, Louisville, Kentucky, 40202, USA
| | - Howard F. Jenkinson
- School of Oral and Dental Sciences, University of Bristol, Lower Maudlin Street, Bristol BS12LY, UK
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209
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Quorum sensing inhibitors: An overview. Biotechnol Adv 2013; 31:224-45. [DOI: 10.1016/j.biotechadv.2012.10.004] [Citation(s) in RCA: 474] [Impact Index Per Article: 43.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Revised: 09/24/2012] [Accepted: 10/30/2012] [Indexed: 12/28/2022]
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210
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Affiliation(s)
- Melissa Ivey
- Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina 27695
| | - Mara Massel
- Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina 27695
| | - Trevor G. Phister
- Division of Food Science, Brewing Science Program, School of Biological Sciences, University of Nottingham, Sutton Bonington LE12 5RD, United Kingdom;
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211
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Brackman G, Al Quntar AAA, Enk CD, Karalic I, Nelis HJ, Van Calenbergh S, Srebnik M, Coenye T. Synthesis and evaluation of thiazolidinedione and dioxazaborocane analogues as inhibitors of AI-2 quorum sensing in Vibrio harveyi. Bioorg Med Chem 2012; 21:660-7. [PMID: 23286963 DOI: 10.1016/j.bmc.2012.11.055] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Revised: 11/26/2012] [Accepted: 11/29/2012] [Indexed: 10/27/2022]
Abstract
Two focused libraries based on two types of compounds, that is, thiazolidinediones and dioxazaborocanes were designed. Structural resemblances can be found between thiazolidinediones and well-known furanone type quorum sensing (QS) inhibitors such as N-acylaminofuranones, and/or acyl-homoserine lactone signaling molecules, while dioxazaborocanes structurally resemble previously reported oxazaborolidine derivatives which antagonized autoinducer 2 (AI-2) binding to its receptor. Because of this, we hypothesized that these compounds could affect AI-2 QS in Vibrio harveyi. Although all compounds blocked QS, the thiazolidinediones were the most active AI-2 QS inhibitors, with EC(50) values in the low micromolar range. Their mechanism of inhibition was elucidated by measuring the effect on bioluminescence in a series of V. harveyi QS mutants and by DNA-binding assays with purified LuxR protein. The active compounds neither affected bioluminescence as such nor the production of AI-2. Instead, our results indicate that the thiazolidinediones blocked AI-2 QS in V. harveyi by decreasing the DNA-binding ability of LuxR. In addition, several dioxazaborocanes were found to block AI-2 QS by targeting LuxPQ.
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Affiliation(s)
- Gilles Brackman
- Laboratory of Pharmaceutical Microbiology, Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium.
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212
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Individual and combined roles of the master regulators AphA and LuxR in control of the Vibrio harveyi quorum-sensing regulon. J Bacteriol 2012. [PMID: 23204455 DOI: 10.1128/jb.01998-12] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Bacteria use a chemical communication process called quorum sensing to control transitions between individual and group behaviors. In the Vibrio harveyi quorum-sensing circuit, two master transcription factors, AphA and LuxR, coordinate the quorum-sensing response. Here we show that AphA regulates 167 genes, LuxR regulates 625 genes, and they coregulate 77 genes. LuxR strongly controls genes at both low cell density and high cell density, suggesting that it is the major quorum-sensing regulator. In contrast, AphA is absent at high cell density and acts to fine-tune quorum-sensing gene expression at low cell density. We examined two loci as case studies of coregulation by AphA and LuxR. First, AphA and LuxR directly regulate expression of the genes encoding the quorum-regulatory small RNAs Qrr2, Qrr3, and Qrr4, the consequence of which is a specifically timed transition between the individual and the group life-styles. Second, AphA and LuxR repress type III secretion system genes but at different times and to different extents. The consequence of this regulation is that type III secretion is restricted to a peak at mid-cell density. Thus, the asymmetric production of AphA and LuxR coupled with differences in their strengths and timing of target gene regulation generate a precise temporal pattern of gene expression.
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213
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Anetzberger C, Reiger M, Fekete A, Schell U, Stambrau N, Plener L, Kopka J, Schmitt-Kopplin P, Hilbi H, Jung K. Autoinducers act as biological timers in Vibrio harveyi. PLoS One 2012; 7:e48310. [PMID: 23110227 PMCID: PMC3482212 DOI: 10.1371/journal.pone.0048310] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 09/24/2012] [Indexed: 12/16/2022] Open
Abstract
Quorum sensing regulates cell density-dependent phenotypes and involves the synthesis, excretion and detection of so-called autoinducers. Vibrio harveyi strain ATCC BAA-1116 (recently reclassified as Vibrio campbellii), one of the best-characterized model organisms for the study of quorum sensing, produces and responds to three autoinducers. HAI-1, AI-2 and CAI-1 are recognized by different receptors, but all information is channeled into the same signaling cascade, which controls a specific set of genes. Here we examine temporal variations of availability and concentration of the three autoinducers in V. harveyi, and monitor the phenotypes they regulate, from the early exponential to the stationary growth phase in liquid culture. Specifically, the exponential growth phase is characterized by an increase in AI-2 and the induction of bioluminescence, while HAI-1 and CAI-1 are undetectable prior to the late exponential growth phase. CAI-1 activity reaches its maximum upon entry into stationary phase, while molar concentrations of AI-2 and HAI-1 become approximately equal. Similarly, autoinducer-dependent exoproteolytic activity increases at the transition into stationary phase. These findings are reflected in temporal alterations in expression of the luxR gene that encodes the master regulator LuxR, and of four autoinducer-regulated genes during growth. Moreover, in vitro phosphorylation assays reveal a tight correlation between the HAI-1/AI-2 ratio as input and levels of receptor-mediated phosphorylation of LuxU as output. Our study supports a model in which the combinations of autoinducers available, rather than cell density per se, determine the timing of various processes in V. harveyi populations.
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Affiliation(s)
- Claudia Anetzberger
- Munich Center for integrated Protein Science at the Department of Biology I, Microbiology, Ludwig-Maximilians-Universität Munich, Germany
| | - Matthias Reiger
- Munich Center for integrated Protein Science at the Department of Biology I, Microbiology, Ludwig-Maximilians-Universität Munich, Germany
| | - Agnes Fekete
- Technische Universität Munich, Chair of Analytical Food Chemistry, Freising, Germany
| | - Ursula Schell
- Munich Center for integrated Protein Science at the Department of Biology I, Microbiology, Ludwig-Maximilians-Universität Munich, Germany
- Max von Pettenkofer-Institut, Ludwig-Maximilians-Universität Munich, Munich, Germany
| | - Nina Stambrau
- Munich Center for integrated Protein Science at the Department of Biology I, Microbiology, Ludwig-Maximilians-Universität Munich, Germany
| | - Laure Plener
- Munich Center for integrated Protein Science at the Department of Biology I, Microbiology, Ludwig-Maximilians-Universität Munich, Germany
| | - Joachim Kopka
- Max-Planck-Institute for Molecular Plant Physiology, Potsdam-Golm, Germany
| | | | - Hubert Hilbi
- Max von Pettenkofer-Institut, Ludwig-Maximilians-Universität Munich, Munich, Germany
| | - Kirsten Jung
- Munich Center for integrated Protein Science at the Department of Biology I, Microbiology, Ludwig-Maximilians-Universität Munich, Germany
- * E-mail:
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214
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Han X, Bai H, Liu L, Dong H, Liu R, Song J, Ding C, Qi K, Liu H, Yu S. The luxS gene functions in the pathogenesis of avian pathogenic Escherichia coli. Microb Pathog 2012; 55:21-7. [PMID: 23046700 DOI: 10.1016/j.micpath.2012.09.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Revised: 09/25/2012] [Accepted: 09/26/2012] [Indexed: 11/24/2022]
Abstract
Avian pathogenic Escherichia coli (APEC) causes avian colibacillosis, the most significant infectious bacterial disease of poultry worldwide. LuxS, the product of the luxS gene, mediates the quorum sensing (QS) mechanism. This involves the production of autoinducer-2 (AI-2), which regulates important physiological traits and a variety of adaptive processes in different bacteria. In this study, a luxS gene deleted APEC mutant strain, ΔDE17, was constructed using strain DE17. Analysis of bioluminescence indicated that deletion of the luxS gene abolished the production of the QS signal AI-2 in the bacteria. Further studies showed that deletion of the luxS gene in DE17 reduced the bacterial virulence by 31.5-fold in ducklings, based on the measurement of the 50% lethal dose. The mutant strain reduced significantly the abilities of adherence and invasion, by 50.0% and 40.7% respectively, compared with the wild strain DE17. The mutant strain also showed reduced survival in vivo: the bacterial loads of the mutant strain in infected liver, spleen and blood were 46.4-fold, 5.2-fold, and 3.7-fold reduced, respectively, compared with the wild-type strain DE17. Real-time polymerase chain reaction (PCR) demonstrated further that the mRNA levels of the virulence-related genes iucD, fyuA, vat, ompA, iss, fimC and tsh were significantly decreased in the mutant strain ΔDE17, when compared with DE17 (p < 0.05). In addition, the deletion of the luxS gene reduced the motility of the bacterium. This study suggests that the luxS gene functions in the pathogenesis of diseases caused by avian pathogenic E. coli.
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Affiliation(s)
- Xiangan Han
- Shanghai Veterinary Research Institute, The Chinese Academy of Agricultural Sciences, Shanghai, PR China
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215
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Li Z, Nair SK. Quorum sensing: how bacteria can coordinate activity and synchronize their response to external signals? Protein Sci 2012; 21:1403-17. [PMID: 22825856 DOI: 10.1002/pro.2132] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Revised: 07/18/2012] [Accepted: 07/18/2012] [Indexed: 01/14/2023]
Abstract
Quorum sensing is used by a large variety of bacteria to regulate gene expression in a cell-density-dependent manner. Bacteria can synchronize population behavior using small molecules called autoinducers that are produced by cognate synthases and recognized by specific receptors. Quorum sensing plays critical roles in regulating diverse cellular functions in bacteria, including bioluminescence, virulence gene expression, biofilm formation, and antibiotic resistance. The best-studied autoinducers are acyl homoserine lactone (AHL) molecules, which are the primary quorum sensing signals used by Gram-negative bacteria. In this review we focus on the AHL-dependent quorum sensing system and highlight recent progress on structural and mechanistic studies of AHL synthases and the corresponding receptors. Crystal structures of LuxI-type AHL synthases provide insights into acyl-substrate specificity, but the current knowledge is still greatly limited. Structural studies of AHL receptors have facilitated a more thorough understanding of signal perception and established the molecular framework for the development of quorum sensing inhibitors.
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Affiliation(s)
- Zhi Li
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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216
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Henares BM, Higgins KE, Boon EM. Discovery of a nitric oxide responsive quorum sensing circuit in Vibrio harveyi. ACS Chem Biol 2012; 7:1331-6. [PMID: 22606970 DOI: 10.1021/cb300215t] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Bacteria use small molecules to assess the density and identity of nearby organisms and formulate a response. This process, called quorum sensing (QS), commonly regulates bioluminescence, biofilm formation, and virulence. Vibrio harveyi have three described QS circuits. Each involves the synthesis of a molecule that regulates phosphorylation of its cognate receptor kinase. Each receptor exchanges phosphate with a common phosphorelay protein, LuxU, which ultimately regulates bioluminescence. Here, we show that another small molecule, nitric oxide (NO), participates in QS through LuxU. V. harveyi display a NO concentration-dependent increase in bioluminescence that is regulated by an hnoX gene. We demonstrate that H-NOX is a NO sensor and NO/H-NOX regulates phosphorylation of a kinase that transfers phosphate to LuxU. This study reveals the discovery of a fourth QS pathway in V. harveyi and suggests that bacteria use QS to integrate not only the density of bacteria but also other diverse information about their environment into decisions about gene expression.
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Affiliation(s)
- Bernadette M. Henares
- Department of Chemistry and Institute of Chemical Biology & Drug Discovery, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Kate E. Higgins
- Department of Chemistry and Institute of Chemical Biology & Drug Discovery, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Elizabeth M. Boon
- Department of Chemistry and Institute of Chemical Biology & Drug Discovery, Stony Brook University, Stony Brook, New York 11794-3400, United States
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217
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Pereira CS, Thompson JA, Xavier KB. AI-2-mediated signalling in bacteria. FEMS Microbiol Rev 2012; 37:156-81. [PMID: 22712853 DOI: 10.1111/j.1574-6976.2012.00345.x] [Citation(s) in RCA: 364] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 06/06/2012] [Accepted: 06/08/2012] [Indexed: 02/06/2023] Open
Abstract
Success in nature depends upon an ability to perceive and adapt to the surrounding environment. Bacteria are not an exception; they recognize and constantly adjust to changing situations by sensing environmental and self-produced signals, altering gene expression accordingly. Autoinducer-2 (AI-2) is a signal molecule produced by LuxS, an enzyme found in many bacterial species and thus proposed to enable interspecies communication. Two classes of AI-2 receptors and many layers and interactions involved in downstream signalling have been identified so far. Although AI-2 has been implicated in the regulation of numerous niche-specific behaviours across the bacterial kingdom, interpretation of these results is complicated by the dual role of LuxS in signalling and the activated methyl cycle, a crucial central metabolic pathway. In this article, we present a comprehensive review of the discovery and early characterization of AI-2, current developments in signal detection, transduction and regulation, and the major studies investigating the phenotypes regulated by this molecule. The development of novel tools should help to resolve many of the remaining questions in the field; we highlight how these advances might be exploited in AI-2 quorum quenching, treatment of diseases, and the manipulation of beneficial behaviours caused by polyspecies communities.
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218
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The multiple signaling systems regulating virulence in Pseudomonas aeruginosa. Microbiol Mol Biol Rev 2012; 76:46-65. [PMID: 22390972 DOI: 10.1128/mmbr.05007-11] [Citation(s) in RCA: 475] [Impact Index Per Article: 39.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cell-to-cell communication is a major process that allows bacteria to sense and coordinately react to the fluctuating conditions of the surrounding environment. In several pathogens, this process triggers the production of virulence factors and/or a switch in bacterial lifestyle that is a major determining factor in the outcome and severity of the infection. Understanding how bacteria control these signaling systems is crucial to the development of novel antimicrobial agents capable of reducing virulence while allowing the immune system of the host to clear bacterial infection, an approach likely to reduce the selective pressures for development of resistance. We provide here an up-to-date overview of the molecular basis and physiological implications of cell-to-cell signaling systems in Gram-negative bacteria, focusing on the well-studied bacterium Pseudomonas aeruginosa. All of the known cell-to-cell signaling systems in this bacterium are described, from the most-studied systems, i.e., N-acyl homoserine lactones (AHLs), the 4-quinolones, the global activator of antibiotic and cyanide synthesis (GAC), the cyclic di-GMP (c-di-GMP) and cyclic AMP (cAMP) systems, and the alarmones guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp), to less-well-studied signaling molecules, including diketopiperazines, fatty acids (diffusible signal factor [DSF]-like factors), pyoverdine, and pyocyanin. This overview clearly illustrates that bacterial communication is far more complex than initially thought and delivers a clear distinction between signals that are quorum sensing dependent and those relying on alternative factors for their production.
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219
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Bojsen RK, Andersen KS, Regenberg B. Saccharomyces cerevisiae— a model to uncover molecular mechanisms for yeast biofilm biology. ACTA ACUST UNITED AC 2012; 65:169-82. [DOI: 10.1111/j.1574-695x.2012.00943.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2011] [Revised: 01/06/2012] [Accepted: 02/09/2012] [Indexed: 01/14/2023]
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220
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Ng WL, Perez L, Cong J, Semmelhack MF, Bassler BL. Broad spectrum pro-quorum-sensing molecules as inhibitors of virulence in vibrios. PLoS Pathog 2012; 8:e1002767. [PMID: 22761573 PMCID: PMC3386246 DOI: 10.1371/journal.ppat.1002767] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Accepted: 05/07/2012] [Indexed: 01/30/2023] Open
Abstract
Quorum sensing (QS) is a bacterial cell-cell communication process that relies on the production and detection of extracellular signal molecules called autoinducers. QS allows bacteria to perform collective activities. Vibrio cholerae, a pathogen that causes an acute disease, uses QS to repress virulence factor production and biofilm formation. Thus, molecules that activate QS in V. cholerae have the potential to control pathogenicity in this globally important bacterium. Using a whole-cell high-throughput screen, we identified eleven molecules that activate V. cholerae QS: eight molecules are receptor agonists and three molecules are antagonists of LuxO, the central NtrC-type response regulator that controls the global V. cholerae QS cascade. The LuxO inhibitors act by an uncompetitive mechanism by binding to the pre-formed LuxO-ATP complex to inhibit ATP hydrolysis. Genetic analyses suggest that the inhibitors bind in close proximity to the Walker B motif. The inhibitors display broad-spectrum capability in activation of QS in Vibrio species that employ LuxO. To the best of our knowledge, these are the first molecules identified that inhibit the ATPase activity of a NtrC-type response regulator. Our discovery supports the idea that exploiting pro-QS molecules is a promising strategy for the development of novel anti-infectives.
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Affiliation(s)
- Wai-Leung Ng
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
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221
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Tabei Y, Ogawa A, Era M, Ninomiya J, Morita H. Influence of cations and anions on the induction of cell density-independent luminescence in Photorhabdus luminescens. J Basic Microbiol 2012; 53:268-76. [PMID: 22733631 DOI: 10.1002/jobm.201100568] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 02/17/2012] [Indexed: 11/12/2022]
Abstract
Bioluminescence is emitted by various living organisms, including bacteria. While the induction mechanism in marine luminescent bacteria, such as Vibrio fischeri and V. harveyi, has been well characterized, this mechanism has not been studied in detail in the non-marine luminescent bacterium Photorhabdus luminescens. Therefore, we investigated the effect of cations and anions on the induction of luminescence by P. luminescens. Cultivation of cells in an inorganic salts solution (ISS) containing KCl, CaCl2 , MgCl2 , NaHCO3 , and MgSO4 resulted in a rapid increase in luminescence intensity. Moreover, the induction of luminescence in the ISS medium was not dependent on cell density, since cell densities remained unchanged during 48 h. Furthermore, we found that compounds containing K(+) , Mg(2+) , and HCO3(-) were necessary to induce cell density-independent luminescence. The intensity of luminescence per cell cultured in medium containing KCl, MgCl2 , and NaHCO3 was approximately 100-fold higher than that cultured in NB. In contrast, when cells actively grew in normal growth condition, the intensity of luminescence per cell was not increased even in the presence of K(+) , Mg(2+) , and HCO3(-) . Thus, these results suggest that the luminescence of P. luminescens is regulated by 2 independent cell density-dependent and -independent mechanisms.
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Affiliation(s)
- Yosuke Tabei
- Faculty of Environmental Engineering, The University of Kitakyushu, 1-1 Hibikino, Wakamatsu-ku, Kitakyushu, Japan
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222
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Beckmann BE, Knoester DB, Connelly BD, Waters CM, McKinley PK. Evolution of resistance to quorum quenching in digital organisms. ARTIFICIAL LIFE 2012; 18:291-310. [PMID: 22662911 PMCID: PMC4138831 DOI: 10.1162/artl_a_00066] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Quorum sensing (QS) is a collective behavior whereby actions of individuals depend on the density of the surrounding population. Bacteria use QS to trigger secretion of digestive enzymes, formation and destruction of biofilms, and, in the case of pathogenic organisms, expression of virulence factors that cause disease. Investigations of mechanisms that prevent or disrupt QS, referred to as quorum quenching, are of interest because they provide a new alternative to antibiotics for treating bacterial infections. Traditional antibiotics either kill bacteria or inhibit their growth, producing selective pressures that promote resistant strains. In contrast, quorum quenching and other so-called anti-infective strategies focus on altering behavior. In this article we evolve QS in populations of digital organisms, a type of self-replicating computer program, and investigate the effects of quorum quenching on these populations. Specifically, we injected the populations with mutant organisms that were impaired in selected ways to disrupt the QS process. The experimental results indicate that the rate at which these mutants are introduced into a population influences both the evolvability of QS and the persistence of an existing QS behavior. Surprisingly, we also observed resistance to quorum quenching. Effectively, populations evolved resistance by reaching quorum at lower cell densities than did the parent strain. Moreover, the level of resistance was highest when the rate of mutant introduction increased over time. These results show that digital organisms can serve as a model to study the evolution and disruption of QS, potentially informing wet-lab studies aimed at identifying targets for anti-infective development.
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223
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Nikaido E, Giraud E, Baucheron S, Yamasaki S, Wiedemann A, Okamoto K, Takagi T, Yamaguchi A, Cloeckaert A, Nishino K. Effects of indole on drug resistance and virulence of Salmonella enterica serovar Typhimurium revealed by genome-wide analyses. Gut Pathog 2012; 4:5. [PMID: 22632036 PMCID: PMC3405474 DOI: 10.1186/1757-4749-4-5] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2012] [Accepted: 05/25/2012] [Indexed: 11/10/2022] Open
Abstract
Background Many Gram-positive and Gram-negative bacteria produce large quantities of indole as an intercellular signal in microbial communities. Indole demonstrated to affect gene expression in Escherichia coli as an intra-species signaling molecule. In contrast to E. coli, Salmonella does not produce indole because it does not harbor tnaA, which encodes the enzyme responsible for tryptophan metabolism. Our previous study demonstrated that E. coli-conditioned medium and indole induce expression of the AcrAB multidrug efflux pump in Salmonella enterica serovar Typhimurium for inter-species communication; however, the global effect of indole on genes in Salmonella remains unknown. Results To understand the complete picture of genes regulated by indole, we performed DNA microarray analysis of genes in the S. enterica serovar Typhimurium strain ATCC 14028s affected by indole. Predicted Salmonella phenotypes affected by indole based on the microarray data were also examined in this study. Indole induced expression of genes related to efflux-mediated multidrug resistance, including ramA and acrAB, and repressed those related to host cell invasion encoded in the Salmonella pathogenicity island 1, and flagella production. Reduction of invasive activity and motility of Salmonella by indole was also observed phenotypically. Conclusion Our results suggest that indole is an important signaling molecule for inter-species communication to control drug resistance and virulence of S. enterica.
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Affiliation(s)
- Eiji Nikaido
- Laboratory of Microbiology and Infectious Diseases, Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-00447, Japan.,Department of Cell Membrane Biology, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan.,Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Etienne Giraud
- INRA, UMR1282 Infectiologie et Santé Publique, F-37380, Nouzilly, France.,Université François Rabelais de Tours, UMR1282 Infectiologie et Santé Publique, F-37000, Tours, France
| | - Sylvie Baucheron
- INRA, UMR1282 Infectiologie et Santé Publique, F-37380, Nouzilly, France.,Université François Rabelais de Tours, UMR1282 Infectiologie et Santé Publique, F-37000, Tours, France
| | - Suguru Yamasaki
- Laboratory of Microbiology and Infectious Diseases, Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-00447, Japan.,Department of Cell Membrane Biology, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan.,Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Agnès Wiedemann
- INRA, UMR1282 Infectiologie et Santé Publique, F-37380, Nouzilly, France.,Université François Rabelais de Tours, UMR1282 Infectiologie et Santé Publique, F-37000, Tours, France
| | - Kousuke Okamoto
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Tatsuya Takagi
- Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Akihito Yamaguchi
- Department of Cell Membrane Biology, Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka, Japan.,Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka, Japan
| | - Axel Cloeckaert
- INRA, UMR1282 Infectiologie et Santé Publique, F-37380, Nouzilly, France.,Université François Rabelais de Tours, UMR1282 Infectiologie et Santé Publique, F-37000, Tours, France
| | - Kunihiko Nishino
- Laboratory of Microbiology and Infectious Diseases, Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-00447, Japan
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Rezzonico F, Smits THM, Duffy B. Detection of AI-2 receptors in genomes of Enterobacteriaceae suggests a role of type-2 quorum sensing in closed ecosystems. SENSORS 2012; 12:6645-65. [PMID: 22778662 PMCID: PMC3386761 DOI: 10.3390/s120506645] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2012] [Revised: 05/11/2012] [Accepted: 05/16/2012] [Indexed: 01/04/2023]
Abstract
The LuxS enzyme, an S-ribosyl-homocysteine lyase, catalyzes the production of the signal precursor for autoinducer-2 mediated quorum sensing (QS-2) in Vibrio. Its widespread occurrence among bacteria is often considered the evidence for a universal language for interspecies communication. Presence of the luxS gene and production of the autoinducer-2 (AI-2) signal have repeatedly been the only evidences presented to assign a functional QS-2 to the most diverse species. In fact, LuxS has a primary metabolic role as part of the activated methyl cycle. In this review we have analyzed the distribution of QS-2 related genes in Enterobacteriaceae by moving the focus of the investigation from AI-2 production to the detection of potential AI-2 receptors. The latter are common in pathogens or endosymbionts of animals, but were also found in a limited number of Enterobacteriaceae of the genera Enterobacter, Klebsiella, and Pantoea that live in close association with plants or fungi. Although a precise function of QS-2 in these species has not been identified, they all show an endophytic or endosymbiontic lifestyle that suggests a role of type-2 quorum sensing in the adaptation to closed ecosystems.
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Affiliation(s)
- Fabio Rezzonico
- Plant Protection Division, Agroscope Changins-Wädenswil ACW, Schloss 1, Wädenswil CH-8820, Switzerland.
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225
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luxS mutant regulation: quorum sensing impairment or methylation disorder? SENSORS 2012; 12:6155-75. [PMID: 22778636 PMCID: PMC3386735 DOI: 10.3390/s120506176] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Revised: 04/12/2012] [Accepted: 04/20/2012] [Indexed: 12/27/2022]
Abstract
AI-2–mediated quorum sensing has been identified in various bacteria, including both Gram-negative and Gram-positive species, and numerous phenotypes have been reported to be regulated by this mechanism, using the luxS-mutant strain. But the AI-2 production process confused this regulatory function; some considered this regulation as the result of a metabolic change, which refers to an important metabolic cycle named activated methyl cycle (AMC), caused by luxS-mutant simultaneously with the defect of AI-2. Herein we hypothesized that the quorum sensing system—not the metabolic aspect—is responsible for such a regulatory function. In this study, we constructed plasmids infused with sahH and induced protein expression in the luxS-mutant strain to make the quorum-sensing system and metabolic system independent. The biofilm-related genes were investigated by real-time polymerase chain reaction (PCR), and the results demonstrated that the quorum-sensing completed strain restored the gene expression of the defective strain, but the metabolically completed one did not. This evidence supported our hypothesis that the autoinducer-2-mediated, quorum-sensing system, not the AMC, was responsible for luxS mutant regulation.
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226
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Crépin A, Barbey C, Beury-Cirou A, Hélias V, Taupin L, Reverchon S, Nasser W, Faure D, Dufour A, Orange N, Feuilloley M, Heurlier K, Burini JF, Latour X. Quorum sensing signaling molecules produced by reference and emerging soft-rot bacteria (Dickeya and Pectobacterium spp.). PLoS One 2012; 7:e35176. [PMID: 22539957 PMCID: PMC3335102 DOI: 10.1371/journal.pone.0035176] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2012] [Accepted: 03/09/2012] [Indexed: 12/30/2022] Open
Abstract
Background Several small diffusible molecules are involved in bacterial quorum sensing and virulence. The production of autoinducers-1 and -2, quinolone, indole and γ-amino butyrate signaling molecules was investigated in a set of soft-rot bacteria belonging to six Dickeya or Pectobacterium species including recent or emerging potato isolates. Methodology/Principal Findings Using bacterial biosensors, immunoassay, and chromatographic analysis, we showed that soft-rot bacteria have the common ability to produce transiently during their exponential phase of growth the N-3-oxo-hexanoyl- or the N-3-oxo-octanoyl-l-homoserine lactones and a molecule of the autoinducer-2 family. Dickeya spp. produced in addition the indole-3-acetic acid in tryptophan-rich conditions. All these signaling molecules have been identified for the first time in the novel Dickeya solani species. In contrast, quinolone and γ-amino butyrate signals were not identified and the corresponding synthases are not present in the available genomes of soft-rot bacteria. To determine if the variations of signal production according to growth phase could result from expression modifications of the corresponding synthase gene, the respective mRNA levels were estimated by reverse transcriptase-PCR. While the N-acyl-homoserine lactone production is systematically correlated to the synthase expression, that of the autoinducer-2 follows the expression of an enzyme upstream in the activated methyl cycle and providing its precursor, rather than the expression of its own synthase. Conclusions/Significance Despite sharing the S-adenosylmethionine precursor, no strong link was detected between the production kinetics or metabolic pathways of autoinducers-1 and -2. In contrast, the signaling pathway of autoinducer-2 seems to be switched off by the indole-3-acetic acid pathway under tryptophan control. It therefore appears that the two genera of soft-rot bacteria have similarities but also differences in the mechanisms of communication via the diffusible molecules. Our results designate autoinducer-1 lactones as the main targets for a global biocontrol of soft-rot bacteria communications, including those of emerging isolates.
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Affiliation(s)
- Alexandre Crépin
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) - Normandie Université - Université de Rouen EA 4312 - IUT Evreux, Evreux, France
- SIPRE Comité Nord Station de Recherche et de Création Variétale, Bretteville du Grand Caux, France
| | - Corinne Barbey
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) - Normandie Université - Université de Rouen EA 4312 - IUT Evreux, Evreux, France
| | - Amélie Beury-Cirou
- SIPRE Comité Nord Station de Recherche et de Création Variétale, Bretteville du Grand Caux, France
- Institut des Sciences du Végétal (ISV) UPR 2355 - CNRS, Gif-sur-Yvette, France
| | - Valérie Hélias
- Fédération Nationale des Producteurs de Plants de Pomme de Terre (FN3PT), Paris, France
- Institut de Génétique Environnement et Protection des Plantes (IGEPP) UMR 1349 - INRA, Rennes, France
| | - Laure Taupin
- Laboratoire de Biotechnologie et Chimie Marines (LBCM) - Université de Bretagne-Sud EA 3884, Lorient, France
| | - Sylvie Reverchon
- Microbiologie Adaptation et Pathogénie (MAP) UMR 5240 - Université Claude Bernard Lyon 1-INSA-CNRS-Bayer CropScience, Villeurbanne, France
| | - William Nasser
- Microbiologie Adaptation et Pathogénie (MAP) UMR 5240 - Université Claude Bernard Lyon 1-INSA-CNRS-Bayer CropScience, Villeurbanne, France
| | - Denis Faure
- Institut des Sciences du Végétal (ISV) UPR 2355 - CNRS, Gif-sur-Yvette, France
| | - Alain Dufour
- Laboratoire de Biotechnologie et Chimie Marines (LBCM) - Université de Bretagne-Sud EA 3884, Lorient, France
| | - Nicole Orange
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) - Normandie Université - Université de Rouen EA 4312 - IUT Evreux, Evreux, France
| | - Marc Feuilloley
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) - Normandie Université - Université de Rouen EA 4312 - IUT Evreux, Evreux, France
| | - Karin Heurlier
- Department of Food Sciences, University of Nottingham, Sutton Bonington, United Kingdom
| | - Jean-François Burini
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) - Normandie Université - Université de Rouen EA 4312 - IUT Evreux, Evreux, France
| | - Xavier Latour
- Laboratoire de Microbiologie Signaux et Microenvironnement (LMSM) - Normandie Université - Université de Rouen EA 4312 - IUT Evreux, Evreux, France
- * E-mail:
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Delcenserie V, LaPointe G, Charaslertrangsi T, Rabalski A, Griffiths MW. Glucose decreases virulence gene expression of Escherichia coli O157:H7. J Food Prot 2012; 75:748-52. [PMID: 22488065 DOI: 10.4315/0362-028x.jfp-11-384] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Escherichia coli O157:H7 is responsible for a human toxico-infection that can lead to severe complications such as hemolytic uremic syndrome. Inside the intestine, E. coli O157:H7 forms typical attaching-effacing lesions and produces Shiga toxins. The genes that are responsible for these lesions are located in a pathogenicity island called the locus of enterocyte effacement (LEE). LEE gene expression is influenced by quorum sensing through the luxS system. In this study, the effect of glucose on the expression of several genes from LEE, on the expression of Shiga toxin genes, and on the expression of luxS was assessed with real-time, reverse transcription PCR. All concentrations of glucose (from 0.1 to 1%) were able to down-regulate genes from the LEE operon. A slight down-regulation of genes implicated in Shiga toxin expression was also observed but was significant for low doses of glucose (0.1 to 0.5%) only. A slight but significant increase in luxS expression was observed with 1% glucose. This confirms that in addition to quorum sensing, the presence or absence of nutrients such as glucose has an impact on the down- or upregulation of LEE-encoded virulence genes by the bacterium. The influence of glucose on the virulence of E. coli O157:H7 has received little attention, and these results suggest that glucose can have an important effect on the virulence of E. coli O157:H7.
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Affiliation(s)
- V Delcenserie
- Department of Food Science, University of Guelph and Canadian Research Institute for Food Safety, Guelph, Ontario, Canada N1G 2W1
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228
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Gölz G, Sharbati S, Backert S, Alter T. Quorum sensing dependent phenotypes and their molecular mechanisms in Campylobacterales. Eur J Microbiol Immunol (Bp) 2012; 2:50-60. [PMID: 24611121 DOI: 10.1556/eujmi.2.2012.1.8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 01/06/2012] [Indexed: 12/26/2022] Open
Abstract
Quorum sensing comprises the mechanism of communication between numerous bacteria via small signalling molecules, termed autoinducers (AI). Using quorum sensing, bacteria can regulate the expression of multiple genes involved in virulence, toxin production, motility, chemotaxis and biofilm formation, thus contributing to adaptation as well as colonisation. The current understanding of the role of quorum sensing in the lifecycle of Campylobacterales is still incomplete. Campylobacterales belong to the class of Epsilonproteobacteria representing a physiologically and ecologically diverse group of bacteria that are rather distinct from the more commonly studied Proteobacteria, such as Escherichia and Salmonella. This review summarises the recent knowledge on distribution and production of AI molecules, as well as possible quorum sensing dependent regulation in the mostly investigated species within the Campylobacterales group: Campylobacter jejuni and Helicobacter pylori.
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229
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Plummer PJ. LuxS and quorum-sensing in Campylobacter. Front Cell Infect Microbiol 2012; 2:22. [PMID: 22919614 PMCID: PMC3417632 DOI: 10.3389/fcimb.2012.00022] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2012] [Accepted: 02/14/2012] [Indexed: 11/13/2022] Open
Abstract
Several intercellular bacterial communication mechanisms have been identified in a broad range of bacterial species. These systems, collectively termed quorum-sensing systems, have been demonstrated to play significant roles in a variety of bacterial processes including motility, biofilm formation, expression of virulence genes, and animal colonization. Campylobacter jejuni is known to possess a LuxS/ autoinducer-2 (AI-2) mediated system that have been partially characterized over the last decade. AI-2 is formed as a byproduct of the activated methyl recycling pathway, specifically by the LuxS enzyme. Previous work in our laboratory and that of others has demonstrated that this gene is involved in a variety of physiologic pathways of C. jejuni including motility, autoagglutination, cytolethal distending toxin (CDT) expression, flagellar expression, oxidative stress, and animal colonization. This review article will summarize the current research associated with LuxS in C. jejuni and will provide insights into the role of this system in the metabolism and intercellular communication of this organism. Additionally, the evidence for other quorum-sensing pathways in Campylobacter will be discussed.
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Affiliation(s)
- Paul J Plummer
- Department of Veterinary Diagnostic and Production Animal Medicine, College of Veterinary Medicine, Iowa State University, Ames IA, USA.
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230
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Imamovic L, Muniesa M. Characterizing RecA-independent induction of Shiga toxin2-encoding phages by EDTA treatment. PLoS One 2012; 7:e32393. [PMID: 22393404 PMCID: PMC3290563 DOI: 10.1371/journal.pone.0032393] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2011] [Accepted: 01/29/2012] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND The bacteriophage life cycle has an important role in Shiga toxin (Stx) expression. The induction of Shiga toxin-encoding phages (Stx phages) increases toxin production as a result of replication of the phage genome, and phage lysis of the host cell also provides a means of Stx toxin to exit the cell. Previous studies suggested that prophage induction might also occur in the absence of SOS response, independently of RecA. METHODOLOGY/PRINCIPAL FINDINGS The influence of EDTA on RecA-independent Stx2 phage induction was assessed, in laboratory lysogens and in EHEC strains carrying Stx2 phages in their genome, by Real-Time PCR. RecA-independent mechanisms described for phage λ induction (RcsA and DsrA) were not involved in Stx2 phage induction. In addition, mutations in the pathway for the stress response of the bacterial envelope to EDTA did not contribute to Stx2 phage induction. The effect of EDTA on Stx phage induction is due to its chelating properties, which was also confirmed by the use of citrate, another chelating agent. Our results indicate that EDTA affects Stx2 phage induction by disruption of the bacterial outer membrane due to chelation of Mg(2+). In all the conditions evaluated, the pH value had a decisive role in Stx2 phage induction. CONCLUSIONS/SIGNIFICANCE Chelating agents, such as EDTA and citrate, induce Stx phages, which raises concerns due to their frequent use in food and pharmaceutical products. This study contributes to our understanding of the phenomenon of induction and release of Stx phages as an important factor in the pathogenicity of Shiga toxin-producing Escherichia coli (STEC) and in the emergence of new pathogenic strains.
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Affiliation(s)
| | - Maite Muniesa
- Department of Microbiology, University of Barcelona, Barcelona, Spain
- * E-mail:
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231
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Taga ME, Xavier KB. Methods for analysis of bacterial autoinducer-2 production. ACTA ACUST UNITED AC 2012; Chapter 1:Unit1C.1. [PMID: 22045583 DOI: 10.1002/9780471729259.mc01c01s23] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Quorum sensing is a cell-cell signaling process that many bacteria use to regulate gene expression as a function of the density of the population. This phenomenon involves the production, release, and response to small chemical molecules termed autoinducers. Most autoinducers are species-specific; however, one autoinducer called autoinducer-2 (AI-2) is produced and detected by many species of bacteria and thus can foster inter-species communication. This unit describes two assays to detect and quantify AI-2 from biological samples. The first uses a bacterial reporter strain, which produces bioluminescence in response to AI-2. The second is an in vitro assay based on a modified version of an AI-2 receptor fused to a cyan fluorescent protein and a yellow fluorescent protein. Binding of AI-2 to this fusion protein induces a dose-dependent decrease in fluorescence resonance energy transfer (FRET), enabling quantification of the AI-2 concentration in the samples.
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Affiliation(s)
- Michiko E Taga
- Department of Plant and Microbial Biology, University of California, Berkeley, California, USA
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232
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Raut N, O'Connor G, Pasini P, Daunert S. Engineered cells as biosensing systems in biomedical analysis. Anal Bioanal Chem 2012; 402:3147-59. [PMID: 22311427 DOI: 10.1007/s00216-012-5756-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2011] [Revised: 01/07/2012] [Accepted: 01/16/2012] [Indexed: 01/08/2023]
Abstract
Over the past two decades there have been great advances in biotechnology, including use of nucleic acids, proteins, and whole cells to develop a variety of molecular analytical tools for diagnostic, screening, and pharmaceutical applications. Through manipulation of bacterial plasmids and genomes, bacterial whole-cell sensing systems have been engineered that can serve as novel methods for analyte detection and characterization, and as more efficient and cost-effective alternatives to traditional analytical techniques. Bacterial cell-based sensing systems are typically sensitive, specific and selective, rapid, easy to use, low-cost, and amenable to multiplexing, high-throughput, and miniaturization for incorporation into portable devices. This critical review is intended to provide an overview of available bacterial whole-cell sensing systems for assessment of a variety of clinically relevant analytes. Specifically, we examine whole-cell sensing systems for detection of bacterial quorum sensing molecules, organic and inorganic toxic compounds, and drugs, and for screening of antibacterial compounds for identification of their mechanisms of action. Methods used in the design and development of whole-cell sensing systems are also reviewed.
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Affiliation(s)
- Nilesh Raut
- Department of Chemistry, University of Kentucky, Lexington, KY 40506, USA
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233
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Bandara HMHN, Lam OLT, Jin LJ, Samaranayake L. Microbial chemical signaling: a current perspective. Crit Rev Microbiol 2012; 38:217-49. [PMID: 22300377 DOI: 10.3109/1040841x.2011.652065] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Communication among microorganisms is mediated through quorum sensing. The latter is defined as cell-density linked, coordinated gene expression in microbial populations as a response to threshold signal concentrations followed by induction of a synchronized population response. This phenomenon is used by a variety of microbes to optimize their survival in a constantly challenging, dynamic milieu, by correlating individual cellular functions to community-based requirements. The synthesis, secretion, and perception of quorum-sensing molecules and their target response play a pivotal role in quorum sensing and are tightly controlled by complex, multilayered and interconnected signal transduction pathways that regulate diverse cellular functions. Quorum sensing exemplifies interactive social behavior innate to the microbial world that controls features such as, virulence, biofilm maturation, antibiotic resistance, swarming motility, and conjugal plasmid transfer. Over the past two decades, studies have been performed to rationalize bacterial cell-to-cell communication mediated by structurally and functionally diverse small molecules. This review describes the theoretical aspects of cellular and quorum-sensing mechanisms that affect microbial physiology and pathobiology.
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Affiliation(s)
- H M H N Bandara
- Oral Biosciences, Prince Philip Dental Hospital, 34, Hospital Road, Sai Ying Pun, Hong Kong
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234
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Yong YC, Zhong JJ. Impacts of quorum sensing on microbial metabolism and human health. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2012; 131:25-61. [PMID: 22767136 DOI: 10.1007/10_2012_138] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Bacteria were considered to be lonely 'mutes' for hundreds of years. However, recently it was found that bacteria usually coordinate their behaviors at the population level by producing (speaking), sensing (listening), and responding to small signal molecules. This so-called quorum sensing (QS) regulation enables bacteria to live in a 'society' with cell-cell communication and controls many important bacterial behaviors. In this chapter, QS systems and their signal molecules for Gram-negative and Gram-positive bacteria are introduced. Most interestingly, QS regulates the important bacterial behaviors such as metabolism and pathogenesis. QS-regulated microbial metabolism includes antibiotic synthesis, pollutant biodegradation, and bioenergy production, which are very relevant to human health. QS is also well-known for its involvement in bacterial pathogenesis, such as iin nfections by Pseudomonas aeruginosa and Staphylococcus aureus. Novel disease diagnosis strategies and antimicrobial agents have also been developed based on QS regulation on bacterial infections. In addition, to meet the requirements for the detection/quantification of QS signaling molecules for research and application, different biosensors have been constructed, which will also be reviewed here. QS regulation is essential to bacterial survival and important to human health. A better understanding of QS could lead better control/manipulation of bacteria, thus making them more helpful to people.
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Affiliation(s)
- Yang-Chun Yong
- Biofuels Institute, School of the Environment, Jiangsu University, 301 Xuefu Road, 212013, Zhenjiang, Jiangsu Province, China
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Cao M, Feng Y, Wang C, Zheng F, Li M, Liao H, Mao Y, Pan X, Wang J, Hu D, Hu F, Tang J. Functional definition of LuxS, an autoinducer-2 (AI-2) synthase and its role in full virulence of Streptococcus suis serotype 2. J Microbiol 2011; 49:1000-11. [PMID: 22203565 DOI: 10.1007/s12275-011-1523-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 12/13/2011] [Indexed: 12/22/2022]
Abstract
Quorum sensing is a widespread chemical communication in response to fluctuation of bacterial population density, and has been implicated into bacterial biofilm formation and regulation of expression of virulence factors. The luxS gene product, S-ribosylhomocysteinase, catalizes the last committed step in biosynthetic pathway of autoinducer 2 (AI-2), a signaling molecule for inter-species quorum sensing. We found a luxS homologue in 05ZYH33, an epidemic strain of Streptococcus suis serotype 2 (SS2) in China. A luxS null mutant (ΔluxS) of 05ZYH33 strain was obtained using an approach of homologous recombination. LuxS was determined to be required for AI-2 production in 05ZYH33 strain of S. suis 2. Inactivation of luxS gene led to a wide range of phenotypic changes including thinner capsular walls, increased tolerance to H(2)O(2), reduced adherence capacity to epithelial cells, etc. In particular, loss of LuxS impaired dramatically its full virulence of SS2 in experimental model of piglets, and functional complementation restored it nearly to the level of parent strain. Genome-wide transcriptome analyses suggested that some known virulence factors such as CPS are down-regulated in the ΔluxS mutant, which might in part explain virulence attenuation by luxS deletion. Similarly, 29 of 71 genes with different expression level were proposed to be targets candidate regulated by LuxS/AI-2-dependent quorum sensing.
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Affiliation(s)
- Min Cao
- Department of Microbiology, Third Military Medical University, Chongqing, P. R. China
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Liu H, Gu D, Cao X, Liu Q, Wang Q, Zhang Y. Characterization of a new quorum sensing regulator luxT and its roles in the extracellular protease production, motility, and virulence in fish pathogen Vibrio alginolyticus. Arch Microbiol 2011; 194:439-52. [PMID: 22130678 DOI: 10.1007/s00203-011-0774-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2011] [Revised: 09/28/2011] [Accepted: 11/07/2011] [Indexed: 11/28/2022]
Abstract
Vibrio alginolyticus, an opportunistic pathogen that causes vibriosis in miscellaneous fish species, has brought about serious economic damage to the mariculture industry in South China. The mechanism of virulence regulation in V. alginolyticus is yet not known except a Vibrio harveyi-like quorum sensing (QS) system that is established to manipulate the expression of diverse genes including those encoding virulence determinants. In this study, a new TetR family QS regulator, luxT, was identified and characterized in V. alginolyticus. The transcription of luxT gene was cell density dependent and was positively regulated by LuxU, an established QS component relaying the signal from three paralleled QS regulatory systems in V. harveyi. In addition, luxT positively regulated both luxO at transcriptional level and luxR at post-transcriptional level, which is thoroughly different from the established QS regulation mode in V. harveyi and Vibrio vulnificus. The mutant of luxT deletion produced markedly decreased total extracellular proteases and reduced motility ability compared to the wild type and the complemented strain luxT (+). The fish infection results indicated that mutation of luxT led to marginal attenuation in the virulence of V. alginolyticus, suggesting that LuxT might play a role in the fine-tuning of the virulence via QS in V. alginolyticus.
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Affiliation(s)
- Huan Liu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China
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Kavanaugh JS, Gakhar L, Horswill AR. The structure of LsrB from Yersinia pestis complexed with autoinducer-2. Acta Crystallogr Sect F Struct Biol Cryst Commun 2011; 67:1501-5. [PMID: 22139152 PMCID: PMC3232125 DOI: 10.1107/s1744309111042953] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 10/17/2011] [Indexed: 11/10/2022]
Abstract
The crystal structure of LsrB from Yersinia pestis complexed with autoinducer-2 (AI-2; space group P2(1)2(1)2(1), unit-cell parameters a = 40.61, b = 61.03, c = 125.23 Å) has been solved by molecular replacement using the structure of LsrB from Salmonella typhimurium (PDB entry 1tjy) and refined to R = 0.180 (R(free) = 0.213) at 1.75 Å resolution. The electron density for bound AI-2 and the stereochemistry of the AI-2-binding site are consistent with bound AI-2 adopting the (2R,4S)-2-methyl-2,3,3,4-tetrahydroxytetrahydrofuran conformation, just as has been observed in the crystal structures of the Salmonella typhimurium and Sinorhizobium meliloti LsrB-AI-2 complexes.
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Affiliation(s)
- Jeffrey S. Kavanaugh
- Microbiology Department, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Lokesh Gakhar
- Protein Crystallography Facility, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
| | - Alexander R. Horswill
- Microbiology Department, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242, USA
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Abstract
AIM This review intends to provide a brief overview regarding quorum sensing among bacteria in biofilms and also attempts to throw light on the new research focusing on interference with the quorum sensing. BACKGROUND Dental plaque is an example of microbial biofilm leading to periodontal disease and dental caries. Quorum sensing is widely employed by a variety of gram-positive and gram-negative bacterial species to coordinate various activities in biofilms. Quorum-sensing-interfering compounds have either a positive or a negative effect on the expression of bacterial phenotypes regulated by quorum sensing. These studies of bacterial quorum sensing have also suggested several ideal targets for drug design which can be promising in preventive and therapeutic aspects of periodontal diseases and dental caries. RESULTS Studies have shown that periodontal disease and dental caries is caused by plaque biofilm bacteria. Quorum sensing is the means of communication between these bacteria to regulate a wide range of behavior patterns among them. The in vitro studies reviewed here have a vital role in opening up this field, because they reveal the basic machinery of cell--cell signaling in microbial communities. The signal machinery bacteria use to coordinate a variety of their activities is identified by these studies. Further, this review aims to discuss several natural and synthetic methods which were used for manipulating bacterial quorum sensing. CONCLUSION The future challenge lies in the ability of the dental research to develop additional mechanisms for interfering with bacterial quorum sensing which can be used as preventive and therapeutic tools for combating oral polymicrobial diseases. CLINICAL SIGNIFICANCE This article aims at reviewing the literature and helping us to understand the ways of communication among bacteria in biofilms, which further open up the prospects in the treatment of diseases caused by biofilms.
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Affiliation(s)
- Baswaraj Biradar
- Department of Prosthodontics, Indira Gandhi Institute of Dental Sciences, Puducherry, India.
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Abstract
Many bacteria use 'quorum sensing' (QS) as a mechanism to regulate gene induction in a population-dependent manner. In its simplest sense this involves the accumulation of a signaling metabolite during growth; the binding of this metabolite to a regulator or multiple regulators activates induction or repression of gene expression. However QS regulation is seldom this simple, because other inputs are usually involved. In this review we have focussed on how those other inputs influence QS regulation and as implied by the title, this often occurs by environmental or physiological effects regulating the expression or activity of the QS regulators. The rationale of this review is to briefly introduce the main QS signals used in Gram-negative bacteria and then introduce one of the earliest understood mechanisms of regulation of the regulator, namely the plant-mediated control of expression of the TraR QS regulator in Agrobacterium tumefaciens. We then describe how in several species, multiple QS regulatory systems can act as integrated hierarchical regulatory networks and usually this involves the regulation of QS regulators. Such networks can be influenced by many different physiological and environmental inputs and we describe diverse examples of these. In the final section, we describe different examples of how eukaryotes can influence QS regulation in Gram-negative bacteria.
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Affiliation(s)
- Marijke Frederix
- Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
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Hooshangi S, Bentley WE. LsrR quorum sensing "switch" is revealed by a bottom-up approach. PLoS Comput Biol 2011; 7:e1002172. [PMID: 21980272 PMCID: PMC3182856 DOI: 10.1371/journal.pcbi.1002172] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Accepted: 07/10/2011] [Indexed: 11/19/2022] Open
Abstract
Quorum sensing (QS) enables bacterial multicellularity and selective advantage for communicating populations. While genetic “switching” phenomena are a common feature, their mechanistic underpinnings have remained elusive. The interplay between circuit components and their regulation are intertwined and embedded. Observable phenotypes are complex and context dependent. We employed a combination of experimental work and mathematical models to decipher network connectivity and signal transduction in the autoinducer-2 (AI-2) quorum sensing system of E. coli. Negative and positive feedback mechanisms were examined by separating the network architecture into sub-networks. A new unreported negative feedback interaction was hypothesized and tested via a simple mathematical model. Also, the importance of the LsrR regulator and its determinant role in the E. coli QS “switch”, normally masked by interfering regulatory loops, were revealed. Our simple model allowed mechanistic understanding of the interplay among regulatory sub-structures and their contributions to the overall native functioning network. This “bottom up” approach in understanding gene regulation will serve to unravel complex QS network architectures and lead to the directed coordination of emergent behaviors. Quorum sensing is a mechanism by which bacterial cells communicate within a population. One particular form of communication in E. coli is through a universal signaling molecule known as autoinducer 2. Although the importance of this form of cell-cell interaction has been recognized in the formation of biofilms and virulent infections, the mechanisms by which this form of communication is regulated is still not well understood. In this paper, we presented a method of unraveling these mechanisms by using a combination of experimental work and mathematical models. We took apart the network architecture and isolated the different components. The examination of these isolated sub-networks provided us with a better understanding of the underlying mechanisms that control and regulate bacterial quorum sensing. We were also able to predict new network interactions with the help of our mathematical models. This bottom up approach, combined with our modeling efforts, proved effective in unraveling the mechanisms of quorum sensing in E. coli.
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Affiliation(s)
- Sara Hooshangi
- College of Professional Studies, The George Washington University, Washington, DC, United States of America
- Fischell Department of Bioengineering, University of Maryland College Park, College Park, Maryland, United States of America
| | - William E. Bentley
- Fischell Department of Bioengineering, University of Maryland College Park, College Park, Maryland, United States of America
- Institute of Bioscience and Biotechnology Research, University of Maryland, College Park, Maryland, United States of America
- * E-mail:
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Active regulation of receptor ratios controls integration of quorum-sensing signals in Vibrio harveyi. Mol Syst Biol 2011; 7:491. [PMID: 21613980 PMCID: PMC3130561 DOI: 10.1038/msb.2011.30] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Accepted: 04/19/2011] [Indexed: 02/07/2023] Open
Abstract
Single-cell quantification of the input–output relation of the quorum-sensing circuit reveals how Vibrio harveyi employs multiple feedback loops to simultaneously control quorum-sensing signal integration and to ensure signal transmission fidelity. We identify the role of multiple feedback loops in the quorum-sensing circuit of the model bacterium, Vibrio harveyi. Single-cell microscopy and genetic analysis demonstrate that a novel feedback loop regulates receptor ratios to control the integration of multiple signals. Quantitative investigation of cells with all feedback loops present as well as mutants with specific feedback loops disrupted reveals that the multiple feedback loops expand the input dynamic range and compress the output dynamic range of signal transmission, and also control the noise level of the output. Our experimental observations can be interpreted in terms of a simple model of the quorum-sensing network. Plotting output after reparameterizing the input variables directly reveals how feedback controls receptors ratios.
Organisms detect multiple environmental cues simultaneously and use the information to coordinate their behaviors. Correctly integrating signals generally requires complex signal transduction pathways (Pawson and Scott, 2010). In addition to accurately integrating signals, regulatory circuits must ensure signal transmission fidelity. Information can be lost or corrupted by internal or external perturbations, so circuits must be designed to function robustly in the presence of such fluctuations. For example, the circadian clock in Neurospora (Virshup and Forger, 2009) and the chemotaxis network in Escherichia coli (Oleksiuk et al, 2011) accurately compensate for temperature variation. However, while signal integration and signal transmission have been addressed separately, little is known about mechanisms cells use to solve both tasks simultaneously. In this study, we report how the model bacterium Vibrio harveyi simultaneously integrates and faithfully transmits multiple chemical signals. In a process called quorum sensing, bacteria communicate by synthesizing, releasing, and detecting signal molecules called autoinducers (AIs). To study the integration of such signals, we studied a strain of V. harveyi that integrates two AI signals into its quorum-sensing circuit: AI-1, an intra-species signal, and AI-2, a ‘universal' inter-species signal. Each signal is detected by a cognate receptor AI-1 by LuxN, and AI-2 by LuxPQ (Figure 4A). The information encoded in the two AIs is transduced through a shared signaling pathway into the master quorum-sensing regulator LuxR. In this study, the AIs serve as inputs and LuxR serves as the output of the quorum-sensing circuit. Interestingly, there are five distinct feedback loops in the V. harveyi quorum-sensing circuit (Figure 4A). How does the circuit use shared components to distinguish between the two AI inputs and what role does each feedback loop have in signal integration and transmission? Using single-cell microscopy, we assayed the activity of the quorum-sensing circuit with a focus on defining the functions of the feedback loops. We quantitatively investigated the signaling input–output relation both in cells with all feedback loops present (Figure 4A) as well as in mutants with specific feedback loops disrupted (Figure 4E, I, M, and Q). We compared the mean LuxR level (Figure 4B, F, J, N, and R) and noise level (Figure 4C, G, K, O, and S) for the input–output relation of five strains. We discovered that the LuxN feedback loop regulates receptor ratios (LuxN to LuxPQ) to control the integration of two signals. We also found that the multiple feedback loops expand the input dynamic range and compress the output dynamic range of signal transmission, and also control the noise in the output. In summary, we used single-cell microscopy to quantify the integration of quorum-sensing signals in V. harveyi. Multiple feedback loops in the quorum-sensing circuit actively regulate receptor ratios to control signal integration, sculpt the input–output dynamic range, and regulate the noise level. This system presents a paradigm for how complex circuitry allows cells to appropriately detect and respond to multiple signals in a dynamically changing environment. Quorum sensing is a chemical signaling mechanism used by bacteria to communicate and orchestrate group behaviors. Multiple feedback loops exist in the quorum-sensing circuit of the model bacterium Vibrio harveyi. Using fluorescence microscopy of individual cells, we assayed the activity of the quorum-sensing circuit, with a focus on defining the functions of the feedback loops. We quantitatively investigated the signaling input–output relation both in cells with all feedback loops present as well as in mutants with specific feedback loops disrupted. We found that one of the feedback loops regulates receptor ratios to control the integration of multiple signals. Together, the feedback loops affect the input–output dynamic range of signal transmission and the noise in the output. We conclude that V. harveyi employs multiple feedback loops to simultaneously control quorum-sensing signal integration and to ensure signal transmission fidelity.
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Mukhopadhyay TK, Allison N, Charlton S, Ward J, Lye GJ. Use of microwells to investigate the effect of quorum sensing on growth and antigen production in Bacillus anthracis Sterne 34F2. J Appl Microbiol 2011; 111:1224-34. [PMID: 21895896 DOI: 10.1111/j.1365-2672.2011.05143.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AIM The aim of this study was to investigate the role of quorum sensing in Bacillus anthracis growth and toxin production. METHODS AND RESULTS A microwell plate culture method was developed to simulate the normal UK-licensed anthrax vaccine production run. Once established, sterile supernatant additions from a previous B. anthracis culture were made, and reductions in lag phase and early stimulation of the anthrax toxin component protective antigen (PA) were monitored using ELISA. The addition of the quorum-sensing inhibitor, fur-1, prolonged the lag phase and impeded PA production. Spin filters of various sizes were used to identify the molecular weight fraction of the sterile supernatant responsible for the autoinducer effect. A weight fraction between 5 and 10 kDa was responsible for the autoinducer effect; however, further identification using mass spectroscopy proved inconclusive. CONCLUSIONS Quorum sensing mediated by the autoinducer two molecule plays a significant role in both B. anthracis growth and toxin production. SIGNIFICANCE AND IMPACT OF THE STUDY While genomic analysis has eluded to the importance of LuxS and quorum sensing in anthrax, this is the first analysis using a production strain of B. anthracis and a quorum-sensing inhibitor to monitor the effect on growth and toxin production. This gives insights into anthrax pathogenicity and vaccine manufacture.
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Affiliation(s)
- T K Mukhopadhyay
- The Advanced Centre for Biochemical Engineering, Department of Biochemical Engineering, University College London, London, UK.
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Wang Y, Zhang W, Wu Z, Zhu X, Lu C. Functional analysis of luxS in Streptococcus suis reveals a key role in biofilm formation and virulence. Vet Microbiol 2011; 152:151-60. [DOI: 10.1016/j.vetmic.2011.04.029] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 03/22/2011] [Accepted: 04/18/2011] [Indexed: 01/03/2023]
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Bodor AM, Jänsch L, Wissing J, Wagner-Döbler I. The luxS mutation causes loosely-bound biofilms in Shewanella oneidensis. BMC Res Notes 2011; 4:180. [PMID: 21663678 PMCID: PMC3146851 DOI: 10.1186/1756-0500-4-180] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Accepted: 06/10/2011] [Indexed: 11/22/2022] Open
Abstract
Background The luxS gene in Shewanella oneidensis was shown to encode an autoinducer-2 (AI-2)-like molecule, the postulated universal bacterial signal, but the impaired biofilm growth of a luxS deficient mutant could not be restored by AI-2, indicating it might not have a signalling role in this organism. Findings Here, we provide further evidence regarding the metabolic role of a luxS mutation in S. oneidensis. We constructed a luxS mutant and compared its phenotype to a wild type control with respect to its ability to remove AI-2 from the medium, expression of secreted proteins and biofilm formation. We show that S. oneidensis has a cell-dependent mechanism by which AI-2 is depleted from the medium by uptake or degradation at the end of the exponential growth phase. As AI-2 depletion is equally active in the luxS mutant and thus does not require AI-2 as an inducer, it appears to be an unspecific mechanism suggesting that AI-2 for S. oneidensis is a metabolite which is imported under nutrient limitation. Secreted proteins were studied by iTraq labelling and liquid chromatography mass spectrometry (LC-MS) detection. Differences between wild type and mutant were small. Proteins related to flagellar and twitching motility were slightly up-regulated in the luxS mutant, in accordance with its loose biofilm structure. An enzyme related to cysteine metabolism was also up-regulated, probably compensating for the lack of the LuxS enzyme. The luxS mutant developed an undifferentiated, loosely-connected biofilm which covered the glass surface more homogenously than the wild type control, which formed compact aggregates with large voids in between. Conclusions The data confirm the role of the LuxS enzyme for biofilm growth in S. oneidensis and make it unlikely that AI-2 has a signalling role in this organism.
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Affiliation(s)
- Agnes M Bodor
- Helmholtz-Centre for Infection Research, Group Microbial Communication, Division of Microbial Pathogenesis, Inhoffenstr, 7, 38124 Braunschweig, Germany.
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Rutherford ST, van Kessel JC, Shao Y, Bassler BL. AphA and LuxR/HapR reciprocally control quorum sensing in vibrios. Genes Dev 2011; 25:397-408. [PMID: 21325136 DOI: 10.1101/gad.2015011] [Citation(s) in RCA: 204] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Bacteria cycle between periods when they perform individual behaviors and periods when they perform group behaviors. These transitions are controlled by a cell-cell communication process called quorum sensing, in which extracellular signal molecules, called autoinducers (AIs), are released, accumulate, and are synchronously detected by a group of bacteria. AI detection results in community-wide changes in gene expression, enabling bacteria to collectively execute behaviors such as bioluminescence, biofilm formation, and virulence factor production. In this study, we show that the transcription factor AphA is a master regulator of quorum sensing that operates at low cell density (LCD) in Vibrio harveyi and Vibrio cholerae. In contrast, LuxR (V. harveyi)/HapR (V. cholerae) is the master regulator that operates at high cell density (HCD). At LCD, redundant small noncoding RNAs (sRNAs) activate production of AphA, and AphA and the sRNAs repress production of LuxR/HapR. Conversely, at HCD, LuxR/HapR represses aphA. This network architecture ensures maximal AphA production at LCD and maximal LuxR/HapR production at HCD. Microarray analyses reveal that 300 genes are regulated by AphA at LCD in V. harveyi, a subset of which is also controlled by LuxR. We propose that reciprocal gradients of AphA and LuxR/HapR establish the quorum-sensing LCD and HCD gene expression patterns, respectively.
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Affiliation(s)
- Steven T Rutherford
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
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Bardill JP, Zhao X, Hammer BK. The Vibrio cholerae quorum sensing response is mediated by Hfq-dependent sRNA/mRNA base pairing interactions. Mol Microbiol 2011; 80:1381-94. [PMID: 21453446 DOI: 10.1111/j.1365-2958.2011.07655.x] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Vibrio cholerae quorum sensing controls expression of four redundant sRNAs, Qrr1-4. The Qrr sRNAs are predicted to alter the translation of several mRNAs, including, hapR, which encodes a transcription factor that controls genes for virulence factors, biofilm formation, protease production and DNA uptake. Each Qrr contains a 21 nucleotide region absolutely conserved among pathogenic Vibrios, and predicted to base pair with mRNA targets, like hapR, aided by the RNA chaperone Hfq. This molecular mechanism was not experimentally tested previously, and we provide here both in vivo and in vitro evidence to validate this model. In Escherichia coli, Qrr expression repressed a HapR-GFP translational fusion, and a specific nucleotide substitution in the 21 nucleotide region eliminated HapR control, while a compensatory mutation in hapR restored it. In V. cholerae, the identical mutations also deregulated HapR-dependent gene expression and corresponding QS phenotypes by altering HapR protein levels. We calculated in vitro binding affinities of a Qrr/hapR complex and show that Hfq stabilizes complex formation. Finally, the Qrr mutation with in vivo defects also prevented Qrr/hapR binding, while the compensatory hapR mutation restored binding. These results demonstrate that the V. cholerae QS response is mediated by base pairing interactions between Qrr sRNAs and hapR mRNA.
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Affiliation(s)
- J Patrick Bardill
- School of Biology, Georgia Institute of Technology, Atlanta, GA 30332-0230, USA
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Yang Q, Han Y, Zhang XH. Detection of quorum sensing signal molecules in the family Vibrionaceae. J Appl Microbiol 2011; 110:1438-48. [PMID: 21395950 DOI: 10.1111/j.1365-2672.2011.04998.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
AIMS The aim of this study was to detect the production of three kinds of quorum sensing (QS) signal molecules, i.e. the N-acyl-homoserine lactone (AHL), the autoinducer-2 (AI-2) and the cholerae autoinducer-1-like (CAI-1-like) molecules in 25 Vibrionaceae strains. METHODS AND RESULTS The QS signal molecules in 25 Vibrionaceae strains were detected with different biosensors. Except Salinivibrio costicola VIB288 and Vibrio natriegens VIB299, all the other 23 Vibrionaceae strains could produce one or more kinds of detectable QS signal molecules. Twenty-one of the 25 strains were found to produce AHL signal molecules by using Vibrio harveyi JMH612 and Agrobacterium tumefaciens KYC55 (pJZ372; pJZ384; pJZ410) as biosensors. The AHL fingerprints of eight strains were detected by thin-layer chromatography with Ag. tumefaciens KYC55, and two of them, i.e. V. mediterranei VIB296 and Aliivibrio logei VIB414 had a high diversity of AHLs. Twenty of the 25 strains were found to have the AI-2 activity, and the luxS gene sequences in 18 strains were proved to be conserved by PCR amplification and sequencing. Only six (five Vibrio strains and A. logei VIB414) of the 25 strains possessed the CAI-1-like activity. A. logei VIB414, V. campbellii VIB285, V. furnissii VIB293, V. pomeroyi LMG20537 and two V. harveyi strains VIB571 and VIB645 were found to produce all the three kinds of QS signal molecules. CONCLUSIONS The results indicated that the QS signal molecules, especially AHL and AI-2 molecules, were widespread in the family Vibrionaceae. SIGNIFICANCE AND IMPACT OF THE STUDY In response to a variety of environmental conditions and selection forces, the family Vibrionaceae produced QS signal molecules with great diversity and complexity. The knowledge we obtained from this study will be useful for further research on the roles of different QS signal molecules in this family.
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Affiliation(s)
- Q Yang
- Key Laboratory of Marine Genetics and Breeding for Ministry of Education, College of Marine Life Sciences, Ocean University of China, Qingdao, China
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Wang Y, Wang H, Cui Z, Chen H, Zhong Z, Kan B, Zhu J. The Prevalence of Functional Quorum-Sensing Systems in Recently Emerged Vibrio cholerae Toxigenic Strains. ENVIRONMENTAL MICROBIOLOGY REPORTS 2011; 3:218-222. [PMID: 21643457 PMCID: PMC3107014 DOI: 10.1111/j.1758-2229.2010.00212.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Vibrio cholerae live in aquatic environments and cause cholera disease. Like many other bacteria, V. cholerae use quorum-sensing (QS) systems to control various cellular functions, such as pathogenesis and biofilm formation. However, some V. cholerae strains are naturally QS-defective, including defective mutations in the quorum sensing master regulator HapR. Here we examined the QS functionality of 602 V. cholerae clinical and environmental strains isolated in China from 1960-2007, by measuring QS-regulated gene expression. We found that a greater percentage of the toxigenic strains (ctxAB(+)) had functional QS as compared to the non-toxigenic strains (ctxAB(-)), and that this trend increased significantly over time. We hypothesize that QS provides adaptive value in V. cholerae pathogenic settings.
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Affiliation(s)
- Yunduan Wang
- Department of Microbiology, MOA Key Lab of Microbiological Engineering of Agricultural Environment, Nanjing Agricultural University, China
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Beijing, China
| | - Hui Wang
- Department of Microbiology, MOA Key Lab of Microbiological Engineering of Agricultural Environment, Nanjing Agricultural University, China
| | - Zhigang Cui
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Beijing, China
| | - Haili Chen
- Department of Microbiology, MOA Key Lab of Microbiological Engineering of Agricultural Environment, Nanjing Agricultural University, China
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Beijing, China
| | - Zengtao Zhong
- Department of Microbiology, MOA Key Lab of Microbiological Engineering of Agricultural Environment, Nanjing Agricultural University, China
| | - Biao Kan
- State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Beijing, China
| | - Jun Zhu
- Department of Microbiology, MOA Key Lab of Microbiological Engineering of Agricultural Environment, Nanjing Agricultural University, China
- Department of Microbiology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104
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Perry J, Koteva K, Wright G. Receptor domains of two-component signal transduction systems. MOLECULAR BIOSYSTEMS 2011; 7:1388-98. [PMID: 21347487 DOI: 10.1039/c0mb00329h] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Two-component signal transduction systems are found ubiquitously in prokaryotes, and in archaea, fungi, yeast and some plants, where they regulate physiologic and molecular processes at both transcriptional and post-transcriptional levels. Two-component systems sense changes in environmental conditions when a specific ligand binds to the receptor domain of the histidine kinase sensory component. The structures of many histidine kinase receptors are known, including those which sense extracellular and cytoplasmic signals. In this review, we discuss the basic architecture of two-component signalling circuits, including known system ligands, structure and function of both receptor and signalling domains, the chemistry of phosphotransfer, and cross-talk between different two-component pathways. Given the importance of these systems in regulating cellular responses, many biochemical techniques have been developed for their study and analysis. We therefore also review current methods used to study two-component signalling, including a new affinity-based proteomics approach used to study inducible resistance to the antibiotic vancomycin through the VanSR two-component signal transduction system.
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Affiliation(s)
- Julie Perry
- MG DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, DeGroote School of Medicine, McMaster University, 1200 Main St W, Hamilton, Ontario, Canada
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LuxS coexpression enhances yields of recombinant proteins in Escherichia coli in part through posttranscriptional control of GroEL. Appl Environ Microbiol 2011; 77:2141-52. [PMID: 21278275 DOI: 10.1128/aem.02347-10] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Cell-to-cell communication, or quorum sensing (QS), enables cell density-dependent regulation of bacterial gene expression which can be exploited for the autonomous-signal-guided expression of recombinant proteins (C. Y. Tsao, S. Hooshangi, H. C. Wu, J. J. Valdes, and W. E. Bentley, Metab. Eng. 12:291-297, 2010). Earlier observations that the metabolic potential of Escherichia coli is conveyed via the QS signaling molecule autoinducer-2 (AI-2) suggested that the capacity for protein synthesis could also be affected by AI-2 signaling (M. P. DeLisa, J. J. Valdes, and W. E. Bentley, J. Bacteriol. 183:2918-2928, 2001). In this work, we found that simply adding conditioned medium containing high levels of AI-2 at the same time as inducing the synthesis of recombinant proteins doubled the yield of active product. We have hypothesized that AI-2 signaling "conditions" cells as a natural consequence of cell-to-cell communication and that this could tweak the signal transduction cascade to alter the protein synthesis landscape. We inserted luxS (AI-2 synthase) into vectors which cosynthesized proteins of interest (organophosphorus hydrolase [OPH], chloramphenicol acetyltransferase [CAT], or UV-variant green fluorescent protein [GFPuv]) and evaluated the protein expression in luxS-deficient hosts. In this way, we altered the level of luxS in the cells in order to "tune" the synthesis of AI-2. We found conditions in which the protein yield was dramatically increased. Further studies demonstrated coincident upregulation of the chaperone GroEL, which may have facilitated higher yields and is shown for the first time to be positively regulated at the posttranscriptional level by AI-2. This report is the first to demonstrate that the protein synthesis capacity of E. coli can be altered by rewiring quorum sensing circuitry.
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