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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

ABSTRACT

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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Available from: Thiba Krishnan
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    • "The online version of this article (doi:10.1007/s13205-015-0348-8) contains supplementary material, which is available to authorized users. raspberry (Vattem et al. 2007), clove (Krishnann et al. 2012). In light of these findings, we look into Ayurveda, the oldest traditional medicine system of India, which reports large number of herbs possessing potential preventive and curative properties (Mukherjee and Wahile 2006). "
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    ABSTRACT: Quorum sensing (QS) plays an important role in virulence of Pseudomonas aeruginosa, blocking of QS ability are viewed as viable antimicrobial chemotherapy and which may prove to be a safe anti-virulent drug. Bioactive components from Piper betle have been reported to possess antimicrobial ability. This study envisages on the anti-QS properties of ethanolic extract of P. betle leaf (PbLE) using P. aeruginosa PAO1 as a model organism. A marked reduction in swarming, swimming, and twitching ability of the bacteria is demonstrated in presence of PbLE. The biofilm and pyocyanin production also shows a marked reduction in presence of PbLE, though it does not affect the bacterial growth. Thus, the studies hint on the possible effect of the bioactive components of PbLE on reducing the virulent ability of the bacteria; identification of bioactive compounds should be investigated further.
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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.
    Full-text · Article · Jul 2015 · Molecular Plant Pathology
    • "A swarming assay was performed on 5 g l À1 agar plates contained 5 g l À1 peptone, 2 g l À1 yeast extract and 10 g l À1 glucose (Kinscherf and Willis 1999) supplemented with sub-MIC of sodium ascorbate. Treated and untreated plates were inoculated with 2 ll of the diluted PAO1 culture and incubated at 37°C for 16 h (Krishnan et al. 2012). "
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    ABSTRACT: AimsQuorum sensing circuits regulate virulence factors in Pseudomonas aeruginosa and coordinate bacterial pathogenicity. We are interested in exploring available medications for their antiquorum sensing activity.Methods and resultsFirst we determined the MIC of ascorbate of P. aeruginosa strain PAO1, and all further experiments used concentrations below the MIC so that results could not be caused by reduced viability. Tests of subinhibitory concentrations of sodium ascorbate on cell signals were performed using a reporter strain assay. Sub-MICs of sodium ascorbate resulted in significant reduction of the signaling molecules C4-HSL and 3-oxo-C12-HSL (P<0.01). The influence of sub-MIC of sodium ascorbate on virulence factors was also determined and ascorbate treatment led to significant depression of elastase, protease and hemolysin activities. In addition, inhibition of pyocyanin production, attenuation of biofilm formation and alteration of Pseudomonas motility were observed. Analysis by RT-PCR tested the effect of ascorbate on the expression of QS regulatory genes. Expression of QS regulatory genes, lasI, lasR, rhlI, rhlR, pqsR and pqsA, was repressed compared to untreated P. aeruginosa PAO1, confirming that ascorbate QS inhibition works on gene expression at the molecular level.Conclusion Sodium ascorbate, even at low concentrations, inhibited QS and related virulence factors of P. aeruginosa PAO1.Significance and impact of the studyThis study demonstrated that sodium ascorbate could function as signal modulator and virulence inhibitor in P. aeruginosa.This article is protected by copyright. All rights reserved.
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