Quorum Quenching Revisited—From Signal Decays to Signalling Confusion

Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia.
Sensors (Impact Factor: 2.25). 12/2012; 12(4):4661-96. DOI: 10.3390/s120404661
Source: PubMed


In a polymicrobial community, while some bacteria are communicating with neighboring cells (quorum sensing), others are interrupting the communication (quorum quenching), thus creating a constant arms race between intercellular communication. In the past decade, numerous quorum quenching enzymes have been found and initially thought to inactivate the signalling molecules. Though this is widely accepted, the actual roles of these quorum quenching enzymes are now being uncovered. Recent evidence extends the role of quorum quenching to detoxification or metabolism of signalling molecules as food and energy source; this includes "signalling confusion", a term coined in this paper to refer to the phenomenon of non-destructive modification of signalling molecules. While quorum quenching has been explored as a novel anti-infective therapy targeting, quorum sensing evidence begins to show the development of resistance against quorum quenching.

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    • "Quorum quenching is defined as a process that inhibits quorum sensing signaling across microbial populations by targeting virulence factors (Kusari et al. 2014a; Hosni et al. 2011). The degradation and/or disruption of autoinducers in a variety of bacterial species utilizing quenching enzymes were recently summarized by Hong et al. (2012). Recognition and subsequent disruption of quorum sensing molecules have been demonstrated by plants. "
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    ABSTRACT: Quorum sensing, the cell-to-cell communication system mediated by autoinducers, is responsible for regulation of virulence factors, infections, invasion, colonization, biofilm formation, and antibiotic resistance within bacterial populations. Concomitantly, quorum quenching is a process that involves attenuation of virulence factors by inhibiting or degrading quorum signaling autoinducers. Survival of endophytic microorganisms, commonly known as endophytes, in planta is a continuous mêlée with invading pathogens and pests. In order to survive in their microhabitats inside plants, endophytes have co-evolved to not only utilize an arsenal of biologically active defense compounds but also impede communication between invading pathogens. Such antivirulence strategies prevent pathogens from communicating with or recognizing each other and thus, colonizing plants. The quenching phenomena often involves microbial crosstalk within single or mixed population(s) vis-à-vis gene expression, and production/modulation of quenching enzymes coupled to various antagonistic and synergistic interactions. This concept is particularly interesting because it can be biotechnologically translated in the future to quorum inhibiting antivirulence therapies without triggering resistance in bacteria, which is currently a major problem worldwide that cannot be tackled only with antimicrobial therapies. In this mini-review, we highlight the quorum quenching capacity of endophytes with respect to attenuation of virulence factors and aiding in plant defense response. Further, benefits and potential challenges of using such systems in biotechnology are discussed.
    Applied Microbiology and Biotechnology 05/2015; 99(13). DOI:10.1007/s00253-015-6660-8 · 3.34 Impact Factor
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    • "ble to impact QS more significantly than free β - CD . The larger 50 nm Si - NPs , in contrast , were able to carry a higher dose of β - CD on fewer nanoparticles , and directly influenced QS in V . fischeri . Previous studies have reported the use of QS antagonists and inhibitors to successfully interfere with bacterial QS ( Dong et al . , 2007 ; Hong et al . , 2012 ; Stacy et al . , 2012 ; Welsh et al . , 2015 ) . QS antagonists are often plant - and algal - based compounds that bind to LuxR - type receptors and prevent the complex from initating QS . Alternatively , QS inhibitors include both natural and synthetic compounds that either degrade ( i . e . , enzymes ) or inhibit HSLs . Many propose t"
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    ABSTRACT: The alarming spread of bacterial resistance to traditional antibiotics has warranted the study of alternative antimicrobial agents. Quorum sensing (QS) is a chemical cell-to-cell communication mechanism utilized by bacteria to coordinate group behaviors and establish infections. QS is integral to bacterial survival, and therefore provides a unique target for antimicrobial therapy. In this study, silicon dioxide nanoparticles (Si-NP) were engineered to target the signaling molecules [i.e., acylhomoserine lactones (HSLs)] used for QS in order to halt bacterial communication. Specifically, when Si-NP were surface functionalized with β-cyclodextrin (β-CD), then added to cultures of bacteria (Vibrio fischeri), whose luminous output depends upon HSL-mediated QS, the cell-to-cell communication was dramatically reduced. Reductions in luminescence were further verified by quantitative polymerase chain reaction (qPCR) analyses of luminescence genes. Binding of HSLs to Si-NPs was examined using nuclear magnetic resonance (NMR) spectroscopy. The results indicated that by delivering high concentrations of engineered NPs with associated quenching compounds, the chemical signals were removed from the immediate bacterial environment. In actively-metabolizing cultures, this treatment blocked the ability of bacteria to communicate and regulate QS, effectively silencing and isolating the cells. Si-NPs provide a scaffold and critical stepping-stone for more pointed developments in antimicrobial therapy, especially with regard to QS—a target that will reduce resistance pressures imposed by traditional antibiotics.
    Frontiers in Microbiology 03/2015; Vol. 6(Article 189):1-7. DOI:10.3389/fmicb.2015.00189 · 3.99 Impact Factor
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    • "Because the AHL signal is a key factor for virulence gene expression in pathogenic bacteria, this signal provides a way to manipulate the QS systems and interrupt communication between bacteria. There are several chemicals and enzymes that target different components of the bacterial QS system to disrupt QS signaling, a process known as quorum quenching (QQ; Hong et al., 2012). The first QQ enzyme, an AHLlactonase , was isolated from Bacillus sp. "
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    ABSTRACT: Microbes and plants have evolved biochemical mechanisms to communicate with each other. The molecules responsible for such communication are secreted during beneficial or harmful interactions. Hundreds of these molecules secreted into the rhizosphere have been identified, and their functions are being studied in order to understand the mechanisms of interaction and communication among the different members of the rhizosphere community. The importance of root and microbe secretion to the underground habitat in improving crop productivity is increasingly recognized, with the discovery and characterization of new secreting compounds found in the rhizosphere. Different "omic" approaches, such as genomics, transcriptomics, proteomics and metabolomics, have expanded our understanding of the first signals between microbes and plants. In this review, we highlight the more recent discoveries related to molecules secreted into the rhizosphere and how they affect plant productivity, either negatively or positively. In addition, we include a survey of novel approaches to studying the rhizosphere and emerging opportunities to direct future studies.
    Plant physiology 08/2014; 166(2). DOI:10.1104/pp.114.241810 · 6.84 Impact Factor
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