151
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Zan J, Cicirelli EM, Mohamed NM, Sibhatu H, Kroll S, Choi O, Choi O, Uhlson CL, Wysoczynski CL, Wysoczinski CL, Murphy RC, Churchill MEA, Hill RT, Fuqua C. A complex LuxR-LuxI type quorum sensing network in a roseobacterial marine sponge symbiont activates flagellar motility and inhibits biofilm formation. Mol Microbiol 2012; 85:916-33. [PMID: 22742196 DOI: 10.1111/j.1365-2958.2012.08149.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Bacteria isolated from marine sponges, including the Silicibacter-Ruegeria (SR) subgroup of the Roseobacter clade, produce N-acylhomoserine lactone (AHL) quorum sensing signal molecules. This study is the first detailed analysis of AHL quorum sensing in sponge-associated bacteria, specifically Ruegeria sp. KLH11, from the sponge Mycale laxissima. Two pairs of luxR and luxI homologues and one solo luxI homologue were identified and designated ssaRI, ssbRI and sscI (sponge-associated symbiont locus A, B and C, luxR or luxI homologue). SsaI produced predominantly long-chain 3-oxo-AHLs and both SsbI and SscI specified 3-OH-AHLs. Addition of exogenous AHLs to KLH11 increased the expression of ssaI but not ssaR, ssbI or ssbR, and genetic analyses revealed a complex interconnected arrangement between SsaRI and SsbRI systems. Interestingly, flagellar motility was abolished in the ssaI and ssaR mutants, with the flagellar biosynthesis genes under strict SsaRI control, and active motility only at high culture density. Conversely, ssaI and ssaR mutants formed more robust biofilms than wild-type KLH11. AHLs and the ssaI transcript were detected in M. laxissima extracts, suggesting that AHL signalling contributes to the decision between motility and sessility and that it may also facilitate acclimation to different environments that include the sponge host.
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Affiliation(s)
- Jindong Zan
- Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, Baltimore, MD 21202, USA
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152
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Garner AL, Kim SK, Zhu J, Struss AK, Watkins R, Feske BD, Kaufmann GF, Janda KD. Stereochemical insignificance discovered in Acinetobacter baumannii quorum sensing. PLoS One 2012; 7:e37102. [PMID: 22629354 PMCID: PMC3358330 DOI: 10.1371/journal.pone.0037102] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 04/17/2012] [Indexed: 11/18/2022] Open
Abstract
Stereochemistry is a key aspect of molecular recognition for biological systems. As such, receptors and enzymes are often highly stereospecific, only recognizing one stereoisomer of a ligand. Recently, the quorum sensing signaling molecules used by the nosocomial opportunistic pathogen, Acinetobacter baumannii, were identified, and the primary signaling molecule isolated from this species was N-(3-hydroxydodecanoyl)-L-homoserine lactone. A plethora of bacterial species have been demonstrated to utilize 3-hydroxy-acylhomoserine lactone autoinducers, and in virtually all cases, the (R)-stereoisomer was identified as the natural ligand and exhibited greater autoinducer activity than the corresponding (S)-stereoisomer. Using chemical synthesis and biochemical assays, we have uncovered a case of stereochemical insignificance in A. baumannii and provide a unique example where stereochemistry appears nonessential for acylhomoserine lactone-mediated quorum sensing signaling. Based on previously reported phylogenetic studies, we suggest that A. baumannii has evolutionarily adopted this unique, yet promiscuous quorum sensing system to ensure its survival, particularly in the presence of other proteobacteria.
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Affiliation(s)
- Amanda L. Garner
- Departments of Chemistry and Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, United States of America
- The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, United States of America
- The Worm Institute for Research and Medicine, The Scripps Research Institute, La Jolla, California, United States of America
| | - Sook Kyung Kim
- Departments of Chemistry and Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, United States of America
- The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Jie Zhu
- Departments of Chemistry and Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, United States of America
- The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Anjali Kumari Struss
- Departments of Chemistry and Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, United States of America
- The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Richard Watkins
- Department of Chemistry, Armstrong Atlantic State University, Savannah, Georgia, United States of America
| | - Brent D. Feske
- Department of Chemistry, Armstrong Atlantic State University, Savannah, Georgia, United States of America
| | - Gunnar F. Kaufmann
- Departments of Chemistry and Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, United States of America
- The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Kim D. Janda
- Departments of Chemistry and Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California, United States of America
- The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California, United States of America
- The Worm Institute for Research and Medicine, The Scripps Research Institute, La Jolla, California, United States of America
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153
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Hodgkinson JT, Galloway WRJD, Wright M, Mati IK, Nicholson RL, Welch M, Spring DR. Design, synthesis and biological evaluation of non-natural modulators of quorum sensing in Pseudomonas aeruginosa. Org Biomol Chem 2012; 10:6032-44. [PMID: 22499353 DOI: 10.1039/c2ob25198a] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Many species of bacteria employ a mechanism of intercellular communication known as quorum sensing which is mediated by small diffusible signalling molecules termed autoinducers. The most common class of autoinducer used by Gram-negative bacteria are N-acylated-L-homoserine lactones (AHLs). Pseudomonas aeruginosa is a clinically important bacterium which is known to use AHL-mediated quorum sensing systems to regulate a variety of processes associated with virulence. Thus the selective disruption of AHL-based quorum sensing represents a strategy to attenuate the pathogenicity of this bacterium. Herein we describe the design, synthesis and biological evaluation of a collection of structurally novel AHL mimics. A number of new compounds capable of modulating the LasR-dependent quorum sensing system of P. aeruginosa were identified, which could have value as molecular tools to study and manipulate this signalling pathway. Worthy of particular note, this research has delivered novel potent quorum sensing antagonists, which strongly inhibit the production of virulence factors in a wild type strain of this pathogenic bacterium.
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Affiliation(s)
- James T Hodgkinson
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, UK
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154
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Bi H, Christensen QH, Feng Y, Wang H, Cronan JE. The Burkholderia cenocepacia BDSF quorum sensing fatty acid is synthesized by a bifunctional crotonase homologue having both dehydratase and thioesterase activities. Mol Microbiol 2012; 83:840-55. [PMID: 22221091 DOI: 10.1111/j.1365-2958.2012.07968.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Signal molecules of the diffusible signal factor (DSF) family have been shown recently to be involved in regulation of pathogenesis and biofilm formation in diverse Gram-negative bacteria. DSF signals are reported to be active not only on their cognate bacteria, but also on unrelated bacteria and the pathogenic yeast, Candida albicans. DSFs are monounsaturated fatty acids of medium chain length containing an unusual cis-2 double bond. Although genetic analyses had identified genes involved in DSF synthesis, the pathway of DSF synthesis was unknown. The DSF of the important human pathogen Burkholderia cenocepacia (called BDSF) is cis-2-dodecenoic acid. We report that BDSF is synthesized from a fatty acid synthetic intermediate, the acyl carrier protein (ACP) thioester of 3-hydroxydodecanoic acid. This intermediate is intercepted by protein Bcam0581 and converted to cis-2-dodecenoyl-ACP. Bcam0581 is annotated as a homologue of crotonase, the first enzyme of the fatty acid degradation pathway. We demonstrated Bcam0581to be a bifunctional protein that not only catalysed dehydration of 3-hydroxydodecanoyl-ACP to cis-2-dodecenoyl-ACP, but also cleaved the thioester bond to give the free acid. Both activities required the same set of active-site residues. Although dehydratase and thioesterase activities are known activities of the crotonase superfamily, Bcam0581 is the first protein shown to have both activities.
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Affiliation(s)
- Hongkai Bi
- Departments of Microbiology Biochemistry, B103 Chemical and Life Sciences Laboratory, University of Illinois, 601 S. Goodwin Ave, Urbana, IL 61801, USA
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155
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Zheng Z, Fuqua C, Chen L. The quorum sensing transcriptional regulator TraR has separate binding sites for DNA and the anti-activator. Biochem Biophys Res Commun 2012; 418:396-401. [PMID: 22274608 DOI: 10.1016/j.bbrc.2012.01.035] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Accepted: 01/07/2012] [Indexed: 10/14/2022]
Abstract
Quorum sensing represents a mechanism by which bacteria control their genetic behaviors via diffusible signals that reflect their population density. TraR, a quorum sensing transcriptional activator in the Rhizobiaceae family, is regulated negatively by the anti-activator TraM via formation of a TraR-TraM heterocomplex. Prior structural analysis suggests that TraM and DNA bind to TraR in distinct sites. Here we combined isothermal titration calorimetry (ITC) and electrophoretic mobility shift assays (EMSA) to investigate roles of TraR residues from Rhizobium sp. NGR234 in binding of both TraM and DNA. We found that K213A mutation of TraR(NGR) abolished DNA binding, however, did not alter TraM binding. Mutations of TraM-interfacing TraR(NGR) residues decreased the TraR-TraM interaction, but did not affect the DNA-binding activity of TraR(NGR). Thus, our biochemical studies support the independent binding sites on TraR for TraM and DNA. We also found that point mutations in TraR(NGR) appeared to decrease the TraR-TraM interaction more effectively than those in TraM(NGR), consistent with structural observations that individual TraR(NGR) residues contact with more TraM(NGR) residues than each TraM(NGR) residues with TraR(NGR) residues. Finally, we showed that TraM inhibition on DNA-binding of TraR was driven thermodynamically. We discussed subtle mechanistic differences in TraM anti-activation on TraR activity between homologous systems.
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Affiliation(s)
- Zhida Zheng
- Department of Molecular and Cellular Biochemistry, 212 S. Hawthorne Dr. Simon Hall 400A, Indiana University, Bloomington, IN 47405, USA
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156
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Boukraa M, Sabbah M, Soulère L, El Efrit ML, Queneau Y, Doutheau A. AHL-dependent quorum sensing inhibition: Synthesis and biological evaluation of α-(N-alkyl-carboxamide)-γ-butyrolactones and α-(N-alkyl-sulfonamide)-γ-butyrolactones. Bioorg Med Chem Lett 2011; 21:6876-9. [DOI: 10.1016/j.bmcl.2011.09.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Revised: 09/01/2011] [Accepted: 09/02/2011] [Indexed: 10/17/2022]
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157
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Crystal structure of QscR, a Pseudomonas aeruginosa quorum sensing signal receptor. Proc Natl Acad Sci U S A 2011; 108:15763-8. [PMID: 21911405 DOI: 10.1073/pnas.1112398108] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Acyl-homoserine lactone (AHL) quorum sensing controls gene expression in hundreds of Proteobacteria including a number of plant and animal pathogens. Generally, the AHL receptors are members of a family of related transcription factors, and although they have been targets for development of antivirulence therapeutics there is very little structural information about this class of bacterial receptors. We have determined the structure of the transcription factor, QscR, bound to N-3-oxo-dodecanoyl-homoserine lactone from the opportunistic human pathogen Pseudomonas aeruginosa at a resolution of 2.55 Å. The ligand-bound QscR is a dimer with a unique symmetric "cross-subunit" arrangement containing multiple dimerization interfaces involving both domains of each subunit. The QscR dimer appears poised to bind DNA. Predictions about signal binding and dimerization contacts were supported by studies of mutant QscR proteins in vivo. The acyl chain of the AHL is in close proximity to the dimerization interfaces. Our data are consistent with an allosteric mechanism of signal transmission in the regulation of DNA binding and thus virulence gene expression.
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158
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Kim J, Kim SK, Grégoire G, Manil B, Schermann JP. Infrared Study of the Bacterial Autoinducer N-Hexanoyl-Homoserine Lactone (C6-HSL) in the Gas-Phase, Water, and Octanol Solutions. J Phys Chem A 2011; 115:9199-206. [DOI: 10.1021/jp205025p] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | - Gilles Grégoire
- Laboratoire de Physique des Lasers, CNRS UMR 7528, Institut Galilée, Université Paris 13, Villetaneuse, 93430, France
| | - Bruno Manil
- Laboratoire de Physique des Lasers, CNRS UMR 7528, Institut Galilée, Université Paris 13, Villetaneuse, 93430, France
| | - Jean Pierre Schermann
- Laboratoire de Physique des Lasers, CNRS UMR 7528, Institut Galilée, Université Paris 13, Villetaneuse, 93430, France
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159
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McInnis CE, Blackwell HE. Design, synthesis, and biological evaluation of abiotic, non-lactone modulators of LuxR-type quorum sensing. Bioorg Med Chem 2011; 19:4812-9. [PMID: 21798749 DOI: 10.1016/j.bmc.2011.06.072] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Revised: 06/22/2011] [Accepted: 06/26/2011] [Indexed: 10/17/2022]
Abstract
Quorum sensing (QS) is a cell-cell signaling mechanism that allows bacteria to monitor their population size and alter their behavior at high cell densities. Gram-negative bacteria use N-acylated L-homoserine lactones (AHLs) as their primary signals for QS. These signals are susceptible to lactone hydrolysis in biologically relevant media, and the ring-opened products are inactive QS signals. We have previously identified a range of non-native AHLs capable of strongly agonizing and antagonizing QS in Gram-negative bacteria. However, these abiotic AHLs are also prone to hydrolysis and inactivation and thereby have a relatively short time window for use (∼12-48 h). Non-native QS modulators with reduced or no hydrolytic instability could have enhanced potencies and would be valuable as tools to study the mechanisms of QS in a range of environments (for example, on eukaryotic hosts). This study reports the design and synthesis of two libraries of new, non-hydrolyzable AHL mimics. The libraries were screened for QS modulatory activity using LasR, LuxR, and TraR bacterial reporter strains, and several new, abiotic agonists and antagonists of these receptors were identified.
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Affiliation(s)
- Christine E McInnis
- Department of Chemistry, University of Wisconsin–Madison, 1101 University Ave., Madison, WI 53706, USA
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160
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Immunomodulatory and protective roles of quorum-sensing signaling molecules N-acyl homoserine lactones during infection of mice with Aeromonas hydrophila. Infect Immun 2011; 79:2646-57. [PMID: 21536794 DOI: 10.1128/iai.00096-11] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Aeromonas hydrophila leads to both intestinal and extraintestinal infections in animals and humans, and the underlying mechanisms leading to mortality are largely unknown. By using a septicemic mouse model of infection, we showed that animals challenged with A. hydrophila die because of kidney and liver damage, hypoglycemia, and thrombocytopenia. Pretreatment of animals with quorum-sensing-associated signaling molecules N-acyl homoserine lactones (AHLs), such as butanoyl and hexanoyl homoserine lactones (C(4)- and C(6)-HSLs), as well as N-3-oxododecanoyl (3-oxo-C(12))-HSL, prevented clinical sequelae, resulting in increased survivability of mice. Since little is known as to how different AHLs modulate the immune response during infection, we treated mice with the above AHLs prior to lethal A. hydrophila infection. When we compared results in such animals to those in controls, the treated animals exhibited a significantly reduced bacterial load in the blood and other mouse organs, as well as various levels of cytokines/chemokines. Importantly, neutrophil numbers were significantly elevated in the blood of C(6)-HSL-treated mice compared to those in animals given phosphate-buffered saline and then infected with the bacteria. These findings coincided with the fact that neutropenic animals were more susceptible to A. hydrophila infection than normal mice. Our data suggested that neutrophils quickly cleared bacteria by either phagocytosis or possibly another mechanism(s) during infection. In a parallel study, we indeed showed that other predominant immune cells inflicted during A. hydrophila infections, such as murine macrophages, when they were pretreated with AHLs, rapidly phagocytosed bacteria, whereas untreated cells phagocytosed fewer bacteria. This study is the first to report that AHL pretreatment modulates the innate immune response in mice and enhances their survivability during A. hydrophila infection.
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161
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Praneenararat T, Beary TMJ, Breitbach AS, Blackwell HE. Synthesis and application of an N-acylated l-homoserine lactone derivatized affinity matrix for the isolation of quorum sensing signal receptors. Bioorg Med Chem Lett 2011; 21:5054-7. [PMID: 21592793 DOI: 10.1016/j.bmcl.2011.04.062] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2011] [Revised: 04/08/2011] [Accepted: 04/12/2011] [Indexed: 01/20/2023]
Abstract
The design and synthesis of an agarose resin functionalized with a Gram-negative quorum sensing (QS) signaling molecule analogue is described. The modified resin was utilized in affinity pull-down assays to successfully isolate QscR, a LuxR-type QS receptor from Pseudomonas aeruginosa. This resin may facilitate the identification of novel QS signal receptors using affinity chromatography techniques.
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Affiliation(s)
- Thanit Praneenararat
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706-1322, USA
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