Inhibition of Quorum Sensing-Controlled Virulence Factor Production in Pseudomonas aeruginosa PAO1 by Ayurveda Spice Clove (Syzygium Aromaticum) Bud Extract

Division of Genetics and Molecular Biology, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia
Sensors (Impact Factor: 2.25). 12/2012; 12(4):4016-30. DOI: 10.3390/s120404016
Source: PubMed


Quorum sensing controls the virulence determinants in most proteobacteria. In this work, the hexane, chloroform and methanol extracts of an Ayurveda spice, namely clove (Syzygium aromaticum), shown anti-quorum sensing activity. Hexane and methanol extracts of clove inhibited the response of C. violaceum CV026 to exogenously supplied N-hexanoylhomoserine lactone, in turn preventing violacein production. Chloroform and methanol extracts of clove significantly reduced bioluminescence production by E. coli [pSB1075] grown in the presence of N-(3-oxododecanoyl)-L-homoserine lactone. We demonstrated that clove extract inhibited quorum sensing-regulated phenotypes in Pseudomonas aeruginosa PA01, including expression of lecA::lux (by hexane extract), swarming (maximum inhibition by methanol extract), pyocyanin (maximum inhibition by hexane extract). This study shows that the presence of natural compounds that exhibit anti-quorum sensing activity in the clove extracts may be useful as the lead of anti-infective drugs.

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    • "The inhibitory effects of CA and SA on the expression of QS-related genes made it reasonable to assume that these compounds might affect directly the accumulation of QS signalling molecules (AHL in Pectobacterium). This hypothesis was confirmed employing two commonly used reporter assays for the presence of AHL molecules (Krishnan et al., 2012; McClean et al., 1997). Our results clearly demonstrate that treatment of PC1 and Pcb1692 with CA and SA reduces the production/accumulation of AHL. "
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    ABSTRACT: Several studies have reported effects of the plant phenolic acids cinnamic acid (CA) and salicylic acid (SA) on virulence of soft rot enterobacteria. However, the mechanisms involved in these processes are not yet fully understood. Here, we investigated whether CA and SA interfere with the quorum-sensing (QS) system of two Pectobacterium species, P. aroidearum and P. carotovorum subsp brasiliense, which are known to produce N-acyl-homoserine lactone (AHL) QS signals. Our results clearly indicate that both phenolic compounds affect the QS machinery of the two species, consequently altering the expression of bacterial virulence factors. While in control treatments, expression of QS-related genes increased over time, exposure of bacteria to nonlethal concentrations of CA or SA inhibited the expression of QS genes, including expI, expR, PC1_1442 (luxR transcriptional regulator) and luxS (a component of the AI-2 system). Other virulence genes known to be regulated by the QS system, such as pecS, pel, peh and yheO, were also down-regulated relative to the control. In agreement with the low levels of expression of expI and expR, CA and SA also reduced the level of AHL signal. The effects of CA and SA on AHL signaling were confirmed in compensation assays, in which exogenous application of N-(β-ketocaproyl)-L-homoserine lactone (eAHL) led to the recovery of the reduction in virulence caused by the two phenolic acids. Collectively, the results of gene expression studies, bioluminescence assays, virulence assays and compensation assays with eAHL clearly support a mechanism by which CA and SA interfere with Pectobacterium virulence via the QS machinery. This article is protected by copyright. All rights reserved.
    Molecular Plant Pathology 07/2015; DOI:10.1111/mpp.12295 · 4.72 Impact Factor
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    • "Since QS regulates a battery of bacterial virulence factors [32], hence this work illustrated the significance in expanding the research on AHL-producing bacteria present in environmental samples. We are currently conducting whole genome sequencing on P. cremoricolorata strain ND07 aiming to study the AHL synthase and receptor genes that will provide more insight into the QS regulatory system in this bacterium. "
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    ABSTRACT: Quorum sensing (QS) is a bacterial cell-to-cell communication system controlling QS-mediated genes which is synchronized with the population density. The regulation of specific gene activity is dependent on the signaling molecules produced, namely N-acyl homoserine lactones (AHLs). We report here the identification and characterization of AHLs produced by bacterial strain ND07 isolated from a Malaysian fresh water sample. Molecular identification showed that strain ND07 is clustered closely to Pseudomonas cremoricolorata. Spent culture supernatant extract of P. cremoricolorata strain ND07 activated the AHL biosensor Chromobacterium violaceum CV026. Using high resolution triple quadrupole liquid chromatography-mass spectrometry, it was confirmed that P. cremoricolorata strain ND07 produced N-octanoyl-l-homoserine lactone (C8-HSL) and N-decanoyl-l-homoserine lactone (C10-HSL). To the best of our knowledge, this is the first documentation on the production of C10-HSL in P. cremoricolorata strain ND07.
    Sensors 07/2014; 14(7):11595-11604. DOI:10.3390/s140711595 · 2.25 Impact Factor
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    • "strain T33 in a dose-dependent manner. In our study, we used the well-known anti-QS compound namely catechin [36] which effectively inhibited the biofilm formation by Vibrio sp. strain T33. "
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    ABSTRACT: N-acylhomoserine lactones (AHL) plays roles as signal molecules in quorum sensing (QS) in most Gram-negative bacteria. QS regulates various physiological activities in relation with population density and concentration of signal molecules. With the aim of isolating marine water-borne bacteria that possess QS properties, we report here the preliminary screening of marine bacteria for AHL production using Chromobacterium violaceum CV026 as the AHL biosensor. Strain T33 was isolated based on preliminary AHL screening and further identified by using 16S rDNA sequence analysis as a member of the genus Vibrio closely related to Vibrio brasiliensis. The isolated Vibrio sp. strain T33 was confirmed to produce N-hexanoyl-l-homoserine lactone (C6-HSL) and N-(3-oxodecanoyl)-l-homoserine lactone (3-oxo-C10 HSL) through high resolution tandem mass spectrometry analysis. We demonstrated that this isolate formed biofilms which could be inhibited by catechin. To the best of our knowledge, this is the first report that documents the production of these AHLs by Vibrio brasiliensis strain T33.
    Sensors 07/2014; 14(7):12104-12113. DOI:10.3390/s140712104 · 2.25 Impact Factor
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