Bacterial Quorum Sensing in Pathogenic Relationships

Division of General Medicine, University of Rochester, Rochester, New York, United States
Infection and Immunity (Impact Factor: 3.73). 10/2000; 68(9):4839-49. DOI: 10.1128/IAI.68.9.4839-4849.2000
Source: PubMed


Bacteria were for a long time believed to exist as individual cells that sought primarily to find nutrients and multiply. The discovery of intercellular communication among bacteria has led to the realization that bacteria are capable of coordinated activity that was once believed to be restricted to multicellular organisms. The capacity to behave collectively as a group has obvious advantages, for example, the ability to migrate to a more suitable environment/better nutrient supply and to adopt new modes of growth, such as sporulation or biofilm formation, which may afford protection from deleterious environments. The "language" used for this intercellular communication is based on small, self-generated signal molecules called autoin- ducers. Through the use of autoinducers, bacteria can regulate their behavior according to population density. The phenom- enon of quorum sensing, or cell-to-cell communication, relies on the principle that when a single bacterium releases autoin- ducers (AIs) into the environment, their concentration is too low to be detected. However, when sufficient bacteria are present, autoinducer concentrations reach a threshold level that allows the bacteria to sense a critical cell mass and, in response, to activate or repress target genes. Most of the bac- teria thus far identified that utilize quorum-sensing systems are associated in some way with plants or animals. The nature of these relationships can be either amicable, as characterized by symbiotic bacteria, or adversarial, as seen with pathogenic bac- teria. There are numerous bacteria that have components of a quorum-sensing system for which the phenotype regulated re- mains an enigma. Similarly, there are bacteria known to reg- ulate a specific phenotype via quorum sensing for which one or more of the regulatory components have thus far eluded iden- tification. In this review we give examples of pathogenic rela- tionships, focusing on organisms for which many of the facets of their quorum-sensing systems have been elucidated.

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Available from: Barbara H Iglewski, Aug 10, 2015
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    • "Quorum sensing (QS) is a population density-dependent regulatory system which regulates a number of crucial processes in various pathogens. QS has been shown to regulate a number of diverse phenotypes in both Gram-negative and Gram-positive bacteria [4] including biofilm formation [5], virulence gene expression [6], and bioluminescence [7]. Bacteria are capable of using small secreted signalling molecules termed autoinducers (AIs) to coordinate group-level behaviors. "
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    ABSTRACT: Quorum sensing has been shown to play a crucial role in Pseudomonas aeruginosa pathogenesis where it activates expression of myriad genes that regulate the production of important virulence factors such as biofilm formation. Antagonism of quorum sensing is an excellent target for antimicrobial therapy and represents a novel approach to combat drug resistance. In this study, Chromobacterium violaceum biosensor strain was employed as a fast, sensitive, reliable, and easy to use tool for rapid screening of soil samples for Quorum Sensing Inhibitors (QSI) and the optimal conditions for maximal QSI production were scrutinized. Screening of 127 soil isolates showed that 43 isolates were able to breakdown the HHL signal. Out of the 43 isolates, 38 isolates were able to inhibit the violet color of the biosensor and to form easily detectable zones of color inhibition around their growth. A confirmatory bioassay was carried out after concentrating the putative positive cell-free lysates. Three different isolates that belonged to Bacillus cereus group were shown to have QSI activities and their QSI activities were optimized by changing their culture conditions. Further experiments revealed that the cell-free lysates of these isolates were able to inhibit biofilm formation by P. aeruginosa clinical isolates. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
    Full-text · Article · Aug 2015 · Journal of Basic Microbiology
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    • "Like other soft rot enterobacteria, Pectobacterium induces characteristic soft rot decay through the disruption of host cell integrity, which is promoted by a variety of plant cell wall-degrading enzymes (PCWDEs) secreted by the bacterium (Davidsson et al., 2013; Toth and Birch, 2005). The synthesis of PCWDEs in Pectobacterium and other soft rot enterobacteria is mediated by quorum sensing (QS) (Barnard and Salmond, 2007; de Kievit and Iglewski, 2000; Pirhonen et al., 1993). QS is a cell-to-cell communication system that allows bacteria to monitor the environment and to modulate gene expression according to population density (Fuqua et al., 1994). "
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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
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    • "Quorum sensing is a process of bacterial communication that relies on the production, detection, and response to extracellular signaling molecules called autoinducers (Fuqua and Greenberg, 2002; Fuqua and Winans, 1994; Waters and Bassler, 2005). Gram-negative bacteria commonly use acyl-homoserine lactone molecules (AHLs) as autoinducers (Bassler, 1999; de Kievit and Iglewski, 2000; Fuqua et al., 1996). In Gram-negative bacteria Aeromonas hydrophila, quorum sensing typically involves the production, release and detection of acylated homoserine lactone signalling molecules called autoinducers. "
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    ABSTRACT: In the Present study, Molecular modelling and structure analysis was performed for S-ribosyl homocysteinase from Aeromonas hydrophila. This is to determine new set of compounds that can be explored as antibiotics sensing and targeting the Quorum sensing proteins. The Probable ligands and their binding sites were also determined using ligprof server. HPS[2-Amino-4-Mercapto-Butyric acid] was found to be the best ligand which can bind to the 3D structure of the target protein. In humans, Aeromonas hydrophila infections are known to cause gastroenteritis and wound infections. Investigations for developing a potential vaccine for its control are underway. Aeromonas hydrophila are ubiquitous, facultative anaerobe, gram-negative bacteria found in fresh, brackish, marine, chlorinated and non-chlorinated water supplies worldwide (Janda 1991, Kaper et al 1980, and Vander Kooj et al 1988). In recent years, a sharp increase in the acute diarrohoeal incidences in human by A. hydrophila has generated a great interest in Aeromonas sp. A. hydrophila is an emergent human pathogen which caused serious health problem regularly around the globe (Janda and Abbott 1998; Abbott et al. 1998; Joseph and Carnahan 2000). The most widely used method for controlling A. hydrophila infections in aquaculture is using antimicrobial drugs. Extensive use of antibiotic has resulted in rapid spread of multi-drug resistant pathogens (Rathore et al, 2006). There is an essential for controlling A. hydrophila infection using different antibiotics which is targeted the speciûc protein/ enzyme of A. hydrophila. Today, there is in an urgent need for novel antibacterial drugs, as many important human pathogens have acquired multiple antibiotic resistance factors. Recently, it has been suggested to develop therapeutics that attack bacterial virulence rather than kill bacteria. Such drugs are called " antipathogenic " and are believed to reduce the development of antibiotic resistance. Specifically, cell-density-dependent gene regulation (quorum-sensing) in bacteria has been proposed as a potential target. While promising
    Full-text · Article · Nov 2014 · Biosciences Biotechnology Research Asia
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