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Kokgan Chan - One of the best experts on this subject based on the ideXlab platform.
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Production of N-acyl Homoserine lactones by Chromobacterium haemolyticum KM2 isolated from the river water in Malaysia.
Archives of microbiology, 2018Co-Authors: Kumutha Priya, Wai-fong Yin, Joanita Sulaiman, Kah Yan How, Kokgan ChanAbstract:Quorum sensing (QS) is a term used to describe cell-to-cell communication that enables bacteria to orchestrate group behaviours according to density of bacterial cells. In Gram-negative bacteria, this signalling system is widely known to regulate a variety of different phenotypes such as antibiotic production and biofilm formation. In this study, we report the production of N-acyl Homoserine lactones produced by Chromobacterium haemolyticum strain KM2, a bacterium isolated from a river water of a reserved tropical national park. Preliminary screening of QS activity using biosensor reporter assays indicated that C. haemolyticum strain KM2 produces both short- and long-chain AHLs. Analysis with high-resolution liquid chromatography–mass spectrometry (LC–MS/MS) analysis revealed the production of three AHLs by strain KM2: N-octanoyl-l-Homoserine lactone (C8-HSL), N-dodecanoyl-l-Homoserine lactone (C12-HSL), and N-3-oxo-dodecanoyl-l-Homoserine lactone (OC12-HSL). This bacterial isolate also exhibited strong β-haemolytic activity. To the best of our knowledge, this is the first documentation of QS activity and multiple AHLs production by C. haemolyticum strain KM2.
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AidP, a novel N-Acyl Homoserine lactonase gene from Antarctic Planococcus sp.
Scientific Reports, 2017Co-Authors: Wah Seng See-too, Wai-fong Yin, Peter Convey, David A. Pearce, Yan-lue Lim, Kokgan ChanAbstract:Planococcus is a Gram-positive halotolerant bacterial genus in the phylum Firmicutes, commonly found in various habitats in Antarctica. Quorum quenching (QQ) is the disruption of bacterial cell-to-cell communication (known as quorum sensing), which has previously been described in mesophilic bacteria. This study demonstrated the QQ activity of a psychrotolerant strain, Planococcus versutus strain L10.15^T, isolated from a soil sample obtained near an elephant seal wallow in Antarctica. Whole genome analysis of this bacterial strain revealed the presence of an N -acyl Homoserine lactonase, an enzyme that hydrolyzes the ester bond of the Homoserine lactone of N -acyl Homoserine lactone (AHLs). Heterologous gene expression in E. coli confirmed its functions for hydrolysis of AHLs, and the gene was designated as aidP ( a uto i nducer d egrading gene from P lanococcus sp.). The low temperature activity of this enzyme suggested that it is a novel and uncharacterized class of AHL lactonase. This study is the first report on QQ activity of bacteria isolated from the polar regions.
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Labrenzia sp. BM1: A Quorum Quenching Bacterium That Degrades N-acyl Homoserine Lactones via Lactonase Activity
Sensors (Basel Switzerland), 2014Co-Authors: Norshazliza Ab Ghani, Wai-fong Yin, Siti Nur Maisarah Norizan, Xin Yue Chan, Kokgan ChanAbstract:We report the degradation of quorum sensing N-acylHomoserine lactone molecules by a bacterium isolated from a Malaysian marine water sample. MALDI-TOF and phylogenetic analysis indicated this isolate BM1 clustered closely to Labrenzia sp. The quorum quenching activity of this isolate was confirmed by using a series of bioassays and rapid resolution liquid chromatography analysis. Labrenzia sp. degraded a wide range of N-acylHomoserine lactones namely N-(3-hexanoyl)-l-Homoserine lactone (C6-HSL), N-(3-oxohexanoyl)-l-Homoserine lactone (3-oxo-C6-HSL) and N-(3-hydroxyhexanoyl)-l-Homoserine lactone (3-hydroxy-C6-HSL). Re-lactonisation bioassays confirmed Labrenzia sp. BM1 degraded these signalling molecules efficiently via lactonase activity. To the best of our knowledge, this is the first documentation of a Labrenzia sp. capable of degrading N-acylHomoserine lactones and confirmation of its lactonase-based mechanism of action.
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quorum sensing activity in pandoraea pnomenusa rb38
Sensors, 2014Co-Authors: Yan-lue Lim, Wai-fong Yin, Linxin Kin, Kokgan ChanAbstract:Strain RB38 was recovered from a former dumping area in Malaysia. MALDI-TOF mass spectrometry and genomic analysis identified strain RB-38 as Pandoraea pnomenusa. Various biosensors confirmed its quorum sensing properties. High resolution triple quadrupole liquid chromatography-mass spectrometry analysis was subsequently used to characterize the N-acyl Homoserine lactone production profile of P. pnomenusa strain RB38, which validated that this isolate produced N-octanoyl Homoserine lactone as a quorum sensing molecule. This is the first report of the production of N-octanoyl Homoserine lactone by P. pnomenusa strain RB38.
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Rhodotorula Mucilaginosa, a Quorum Quenching Yeast Exhibiting Lactonase Activity Isolated from a Tropical Shoreline
MDPI AG, 2014Co-Authors: Norshazliza Ab Ghani, Wai-fong Yin, Xin Yue Chan, Joanita Sulaiman, Zahidah Ismail, Kokgan ChanAbstract:Two microbial isolates from a Malaysian shoreline were found to be capable of degrading N-acylHomoserine lactones. Both Matrix Assisted Laser Desorption Ionization-Time of Flight-Mass Spectrometry and 18S rDNA phylogenetic analyses confirmed that these isolates are Rhodotorula mucilaginosa. Quorum quenching activities were detected by a series of bioassays and rapid resolution liquid chromatography analysis. The isolates were able to degrade various quorum sensing molecules namely N-hexanoyl-L-Homoserine lactone (C6-HSL), N-(3-oxo-hexanoyl)-L-Homoserine lactone (3-oxo-C6-HSL) and N-(3-hydroxyhexanoyl)-L-Homoserine lactone (3-hydroxy-C6-HSL). Using a relactonisation assay to verify the quorum quenching mechanism, it is confirmed that Rh. mucilaginosa degrades the quorum sensing molecules via lactonase activity. To the best of our knowledge, this is the first documentation of the fact that Rh. mucilaginosa has activity against a broad range of AHLs namely C6-HSL, 3-oxo-C6-HSL and 3-hydroxy-C6-HSL
Peter E Greenberg - One of the best experts on this subject based on the ideXlab platform.
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virulence of burkholderia mallei quorum sensing mutants
Infection and Immunity, 2013Co-Authors: Charlotte D Majerczyk, Loren Kinman, Richard C Bunt, Peter E GreenbergAbstract:ABSTRACT Many Proteobacteria use acyl-Homoserine lactone-mediated quorum-sensing (QS) to activate specific sets of genes as a function of cell density. QS often controls the virulence of pathogenic species, and in fact a previous study indicated that QS was important for Burkholderia mallei mouse lung infections. To gain in-depth information on the role of QS in B. mallei virulence, we constructed and characterized a mutant of B. mallei strain GB8 that was unable to make acyl-Homoserine lactones. The QS mutant showed virulence equal to that of its wild-type parent in an aerosol mouse infection model, and growth in macrophages was indistinguishable from that of the parent strain. Furthermore, we assessed the role of QS in B. mallei ATCC 23344 by constructing and characterizing a mutant strain producing AiiA, a lactonase enzyme that degrades acyl-Homoserine lactones. Although acyl-Homoserine lactone levels in cultures of this strain are very low, it showed full virulence. Contrary to the previous report, we conclude that QS is not required for acute B. mallei infections of mice. QS may be involved in some stage of chronic infections in the natural host of horses, or the QS genes may be remnants of the QS network in B. pseudomallei from which this host-adapted pathogen evolved.
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a distinct qscr regulon in the pseudomonas aeruginosa quorum sensing circuit
Journal of Bacteriology, 2006Co-Authors: Yannick Lequette, Joon Hee Lee, Fouzia Ledgham, Andree Lazdunski, Peter E GreenbergAbstract:The opportunistic pathogen Pseudomonas aeruginosa possesses two complete acyl-Homoserine lactone (acyl-HSL) signaling systems. One system consists of LasI and LasR, which generate a 3-oxododecanoyl-Homoserine lactone signal and respond to that signal, respectively. The other system is RhlI and RhlR, which generate butanoyl-Homoserine lactone and respond to butanoyl-Homoserine lactone, respectively. These quorum-sensing systems control hundreds of genes. There is also an orphan LasR-RhlR homolog, QscR, for which there is no cognate acyl-HSL synthetic enzyme. We previously reported that a qscR mutant is hypervirulent and showed that QscR transiently represses a few quorum-sensing-controlled genes. To better understand the role of QscR in P. aeruginosa gene regulation and to better understand the relationship between QscR, LasR, and RhlR control of gene expression, we used transcription profiling to identify a QscR-dependent regulon. Our analysis revealed that QscR activates some genes and represses others. Some of the repressed genes are not regulated by the LasR-I or RhlR-I systems, while others are. The LasI-generated 3-oxododecanoyl-Homoserine lactone serves as a signal molecule for QscR. Thus, QscR appears to be an integral component of the P. aeruginosa quorum-sensing circuitry. QscR uses the LasI-generated acyl-Homoserine lactone signal and controls a specific regulon that overlaps with the already overlapping LasR- and RhlR-dependent regulons.
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a network of networks quorum sensing gene regulation in pseudomonas aeruginosa
International Journal of Medical Microbiology, 2006Co-Authors: Martin Schuster, Peter E GreenbergAbstract:The opportunistic pathogen Pseudomonas aeruginosa possesses two N-acyl-Homoserine lactone quorum-sensing systems that regulate large, overlapping sets of genes. Recent global transcriptome and proteome analyses provided a wealth of information about the identity of the regulated genes, N-acyl-Homoserine lactone signal specificity, timing of induction, and environmental effects on gene expression. Quorum-sensing gene expression in P. aeruginosa is also embedded in a highly interconnected network of other regulatory systems with a high potential for integrating and responding to multiple environmental signals. Such epigenetic complexity may constitute the basis for the exceptional adaptibility of P. aeruginosa to diverse environments.
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quinolone signaling in the cell to cell communication system of pseudomonas aeruginosa
Proceedings of the National Academy of Sciences of the United States of America, 1999Co-Authors: Everett C Pesci, Peter E Greenberg, Jared B J Milbank, James P Pearson, Susan L Mcknight, Andrew S Kende, Barbara H IglewskiAbstract:Numerous species of bacteria use an elegant regulatory mechanism known as quorum sensing to control the expression of specific genes in a cell-density dependent manner. In Gram-negative bacteria, quorum sensing systems function through a cell-to-cell signal molecule (autoinducer) that consists of a Homoserine lactone with a fatty acid side chain. Such is the case in the opportunistic human pathogen Pseudomonas aeruginosa, which contains two quorum sensing systems (las and rhl) that operate via the autoinducers, N-(3-oxododecanoyl)-l-Homoserine lactone and N-butyryl-l-Homoserine lactone. The study of these signal molecules has shown that they bind to and activate transcriptional activator proteins that specifically induce numerous P. aeruginosa virulence genes. We report here that P. aeruginosa produces another signal molecule, 2-heptyl-3-hydroxy-4-quinolone, which has been designated as the Pseudomonas quinolone signal. It was found that this unique cell-to-cell signal controlled the expression of lasB, which encodes for the major virulence factor, LasB elastase. We also show that the synthesis and bioactivity of Pseudomonas quinolone signal were mediated by the P. aeruginosa las and rhl quorum sensing systems, respectively. The demonstration that 2-heptyl-3-hydroxy-4-quinolone can function as an intercellular signal sheds light on the role of secondary metabolites and shows that P. aeruginosa cell-to-cell signaling is not restricted to acyl-Homoserine lactones.
Everett P. Greenberg - One of the best experts on this subject based on the ideXlab platform.
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Long-Chain Acyl-Homoserine Lactone Quorum-Sensing Regulation of Rhodobacter capsulatus Gene Transfer Agent Production
Journal of bacteriology, 2002Co-Authors: Amy L Schaefer, Terumi A. Taylor, J. Thomas Beatty, Everett P. GreenbergAbstract:Many proteobacteria use acyl-Homoserine lactones as quorum-sensing signals. Traditionally, biological detection systems have been used to identify bacteria that produce acyl-Homoserine lactones, although the specificities of these detection systems can limit discovery. We used a sensitive approach that did not require a bioassay to detect production of long-acyl-chain Homoserine lactone production by Rhodobacter capsulatus and Paracoccus denitrificans. These long-chain acyl-Homoserine lactones are not readily detected by standard bioassays. The most abundant acyl-Homoserine lactone was N-hexadecanoyl-Homoserine lactone. The long-chain acyl-Homoserine lactones were concentrated in cells but were also found in the culture fluid. An R. capsulatus gene responsible for long-chain acyl-Homoserine lactone synthesis was identified. A mutation in this gene, which we named gtaI, resulted in decreased production of the R. capsulatus gene transfer agent, and gene transfer agent production was restored by exogenous addition of N-hexadecanoyl-Homoserine lactone. Thus, long-chain acyl-Homoserine lactones serve as quorum-sensing signals to enhance genetic exchange in R. capsulatus.
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Generation of cell-to-cell signals in quorum sensing: acyl Homoserine lactone synthase activity of a purified Vibrio fischeri LuxI protein.
Proceedings of the National Academy of Sciences of the United States of America, 1996Co-Authors: Amy L Schaefer, Dale L. Val, Brian L. Hanzelka, John E. Cronan, Everett P. GreenbergAbstract:Abstract Many bacteria use acyl Homoserine lactone signals to monitor cell density in a type of gene regulation termed quorum sensing and response. Synthesis of these signals is directed by homologs of the luxi gene of Vibrio fischeri. This communication resolves two critical issues concerning the synthesis of the V. fischeri signal. (i) The luxI product is directly involved in signal synthesis-the protein is an acyl Homoserine lactone synthase; and (ii) the substrates for acyl Homoserine lactone synthesis are not amino acids from biosynthetic pathways or fatty acid degradation products, but rather they are S-adenosylmethionine (SAM) and an acylated acyl carrier protein (ACP) from the fatty acid biosynthesis pathway. We purified a maltose binding protein-LuxI fusion polypeptide and showed that, when provided with the appropriate substrates, it catalyzes the synthesis of an acyl Homoserine lactone. In V. fischeri, luxi directs the synthesis of N-(3-oxohexanoyl) Homoserine lactone and hexanoyl Homoserine lactone. The purified maltose binding protein-LuxI fusion protein catalyzes the synthesis of hexanoyl Homoserine lactone from hexanoyl-ACP and SAM. There is a high level of specificity for hexanoyl-ACP over ACPs with differing acyl group lengths, and hexanoyl Homoserine lactone was not synthesized when SAM was replaced with other amino acids, such as methionine, S-adenosylhomocysteine, Homoserine, or Homoserine lactone, or when hexanoyl-SAM was provided as the substrate. This provides direct evidence that the LuxI protein is an auto-inducer synthase that catalyzes the formation of an amide bond between SAM and a fatty acyl-ACP and then catalyzes the formation of the acyl Homoserine lactone from the acyl-SAM intermediate.
Amy L Schaefer - One of the best experts on this subject based on the ideXlab platform.
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Long-Chain Acyl-Homoserine Lactone Quorum-Sensing Regulation of Rhodobacter capsulatus Gene Transfer Agent Production
Journal of bacteriology, 2002Co-Authors: Amy L Schaefer, Terumi A. Taylor, J. Thomas Beatty, Everett P. GreenbergAbstract:Many proteobacteria use acyl-Homoserine lactones as quorum-sensing signals. Traditionally, biological detection systems have been used to identify bacteria that produce acyl-Homoserine lactones, although the specificities of these detection systems can limit discovery. We used a sensitive approach that did not require a bioassay to detect production of long-acyl-chain Homoserine lactone production by Rhodobacter capsulatus and Paracoccus denitrificans. These long-chain acyl-Homoserine lactones are not readily detected by standard bioassays. The most abundant acyl-Homoserine lactone was N-hexadecanoyl-Homoserine lactone. The long-chain acyl-Homoserine lactones were concentrated in cells but were also found in the culture fluid. An R. capsulatus gene responsible for long-chain acyl-Homoserine lactone synthesis was identified. A mutation in this gene, which we named gtaI, resulted in decreased production of the R. capsulatus gene transfer agent, and gene transfer agent production was restored by exogenous addition of N-hexadecanoyl-Homoserine lactone. Thus, long-chain acyl-Homoserine lactones serve as quorum-sensing signals to enhance genetic exchange in R. capsulatus.
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Generation of cell-to-cell signals in quorum sensing: acyl Homoserine lactone synthase activity of a purified Vibrio fischeri LuxI protein.
Proceedings of the National Academy of Sciences of the United States of America, 1996Co-Authors: Amy L Schaefer, Dale L. Val, Brian L. Hanzelka, John E. Cronan, Everett P. GreenbergAbstract:Abstract Many bacteria use acyl Homoserine lactone signals to monitor cell density in a type of gene regulation termed quorum sensing and response. Synthesis of these signals is directed by homologs of the luxi gene of Vibrio fischeri. This communication resolves two critical issues concerning the synthesis of the V. fischeri signal. (i) The luxI product is directly involved in signal synthesis-the protein is an acyl Homoserine lactone synthase; and (ii) the substrates for acyl Homoserine lactone synthesis are not amino acids from biosynthetic pathways or fatty acid degradation products, but rather they are S-adenosylmethionine (SAM) and an acylated acyl carrier protein (ACP) from the fatty acid biosynthesis pathway. We purified a maltose binding protein-LuxI fusion polypeptide and showed that, when provided with the appropriate substrates, it catalyzes the synthesis of an acyl Homoserine lactone. In V. fischeri, luxi directs the synthesis of N-(3-oxohexanoyl) Homoserine lactone and hexanoyl Homoserine lactone. The purified maltose binding protein-LuxI fusion protein catalyzes the synthesis of hexanoyl Homoserine lactone from hexanoyl-ACP and SAM. There is a high level of specificity for hexanoyl-ACP over ACPs with differing acyl group lengths, and hexanoyl Homoserine lactone was not synthesized when SAM was replaced with other amino acids, such as methionine, S-adenosylhomocysteine, Homoserine, or Homoserine lactone, or when hexanoyl-SAM was provided as the substrate. This provides direct evidence that the LuxI protein is an auto-inducer synthase that catalyzes the formation of an amide bond between SAM and a fatty acyl-ACP and then catalyzes the formation of the acyl Homoserine lactone from the acyl-SAM intermediate.
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quorum sensing in vibrio fischeri probing autoinducer luxr interactions with autoinducer analogs
Journal of Bacteriology, 1996Co-Authors: Amy L Schaefer, Brian L. Hanzelka, A Eberhard, E P GreenbergAbstract:The Vibrio fischeri luminescence genes are activated by the transcription factor LuxR in combination with a diffusible signal compound, N-(3-oxohexanoyl) Homoserine lactone, termed the autoinducer. We have synthesized a set of autoinducer analogs. Many analogs with alterations in the acyl side chain showed evidence of binding to LuxR. Some appeared to bind with an affinity similar to that of the autoinducer, but none showed a higher affinity, and many did not bind as tightly as the autoinducer. For the most part, compounds with substitutions in the Homoserine lactone ring did not show evidence of binding to LuxR. The exceptions were compounds with a homocysteine thiolactone ring in place of the Homoserine lactone ring. Many but not all of the analogs showing evidence of LuxR binding had some ability to activate the luminescence genes. None were as active as the autoinducer. While most showed little ability to induce luminescence, a few analogs with rather conservative substitutions had appreciable activity. Under the conditions we employed, some of the analogs showing little or no ability to induce luminescence were inhibitors of the autoinducer.
Alan H. Fairlamb - One of the best experts on this subject based on the ideXlab platform.
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Homoserine and quorum sensing acyl Homoserine lactones as alternative sources of threonine a potential role for Homoserine kinase in insect stage trypanosoma brucei
Molecular Microbiology, 2015Co-Authors: Han B. Ong, Wai S. Lee, Stephen Patterson, Susan Wyllie, Alan H. FairlambAbstract:Summary De novo synthesis of threonine from aspartate occurs via the β-aspartyl phosphate pathway in plants, bacte- ria and fungi. However, the Trypanosoma brucei genome encodes only the last two steps in this pathway: Homoserine kinase (HSK) and threonine syn- thase. Here, we investigated the possible roles for this incomplete pathway through biochemical, genetic and nutritional studies. Purified recombinant TbHSK spe- cifically phosphorylates L-Homoserine and displays kinetic properties similar to other HSKs. HSK null mutants generated in bloodstream forms displayed no growth phenotype in vitro or loss of virulence in vivo. However, following transformation into procyclic forms, Homoserine, Homoserine lactone and certain acyl Homoserine lactones (AHLs) were found to sub- stitute for threonine in growth media for wild-type procyclics, but not HSK null mutants. The tsetse fly is considered to be an unlikely source of these nutrients as it feeds exclusively on mammalian blood. Bioinfor- matic studies predict that tsetse endosymbionts possess part (up to Homoserine in Wigglesworthia glossinidia) or all of the β-aspartyl phosphate pathway (Sodalis glossinidius). In addition S. glossinidius is known to produce 3-oxohexanoylHomoserine lactone which also supports trypanosome growth. We propose thatT. brucei has retained HSK and threonine synthase in order to salvage these nutrients when threonine availability is limiting.
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Conference summary
2012Co-Authors: Han B. Ong, Wai S. Lee, Stephen Patterson, Susan Wyllie, Alan H. FairlambAbstract:Homoserine and quorum-sensing acyl Homoserine lactones as alternative sources of threonine: a potential role for Homoserine kinase in insect-stage Trypanosoma bruce