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Special Issue "Microbial Quorum Sensing: Linking the Outside World to Microbial Behaviour"

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A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Biosensors".

Deadline for manuscript submissions: closed (15 January 2012)

Special Issue Editor

Guest Editor
Prof. Dr. Tom Coenye

Laboratory of Pharmaceutical Microbiology, Ghent University, Harelbekestraat 72, B-9000 Gent, Belgium
Website | E-Mail
Phone: Tel: 32 - (0) 9 264 81 41 Fax: 32 - (0) 9 264 81 9
Fax: +32 9 2648195
Interests: bacterial quorum sensing; biofilm formation; biofouling

Special Issue Information

Dear Colleagues,

Bacteria “communicate” with each other by using signalling molecules, a process called “quorum sensing” (QS). This form of signal dependent communication is present in Gram-positive and Gram-negative bacteria, as well as in fungi. At low population density only basal amounts of signal molecules are produced, not provoking an effect. At a certain threshold, signal concentrations will be high enough resulting in a binding to signal receptors and ultimately in an altered gene expression. Many micro-organisms apply their QS system(s) for the coordination of virulence and biofilm formation and/or maturation. The most commonly-used signaling molecules are N-acyl-homoserine lactones (AHL) that are produced by many Gram-negative bacteria. The autoinducer-2 (AI-2) QS system is considered to be a universal system used for interspecies communication and allows bacteria not only to sense the density of members of their own species, but also to sense the total density of a mixed community. The QS system of Gram-positive bacteria generally consists of a signal peptide and a two-component regulatory system made up of a membrane-bound sensor and an intracellular response regulator. QS systems in Gram-positive bacteria are much more diverse than the Gram-negative AHL QS system and there are many variations in the nature of the QS signal. In addition, some bacteria use alfa-hydroxy-ketone signaling molecules (including cholera autoinducer 1 and Legionella autoinducer 2), signaling molecules belonging to the "diffusible signal factor" family or quinolones of the PQS family. Finally, signaling molecules like tyrosol and farnesol can be sensed by fungi and can regulate group behaviour in these organisms.
This special issue of "Sensors" aims to cover the different aspects of cell-cell communication and how microorganisms use this quorum sensing to regulate their behaviour.

Prof. Dr. Tom Coenye
Guest Editor

Keywords

  • alfa-keto-hydroxyketones
  • autoinducer 2
  • autoinducing peptides
  • cell-cell communication
  • cholera autoinducer 1
  • diffusible signal factor
  • efficiency sensing
  • farnesol
  • N-acyl homoserine lactone
  • Pseudomonas quinolone signal
  • quorum quenching
  • quorum sensing
  • tyrosol

Published Papers (16 papers)

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Research

Jump to: Review

Open AccessArticle CMEIAS-Aided Microscopy of the Spatial Ecology of Individual Bacterial Interactions Involving Cell-to-Cell Communication within Biofilms
Sensors 2012, 12(6), 7047-7062; doi:10.3390/s120607047
Received: 29 March 2012 / Revised: 17 April 2012 / Accepted: 22 May 2012 / Published: 29 May 2012
Cited by 4 | PDF Full-text (1274 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes how the quantitative analytical tools of CMEIAS image analysis software can be used to investigate in situ microbial interactions involving cell-to-cell communication within biofilms. Various spatial pattern analyses applied to the data extracted from the 2-dimensional coordinate positioning of individual
[...] Read more.
This paper describes how the quantitative analytical tools of CMEIAS image analysis software can be used to investigate in situ microbial interactions involving cell-to-cell communication within biofilms. Various spatial pattern analyses applied to the data extracted from the 2-dimensional coordinate positioning of individual bacterial cells at single-cell resolution indicate that microbial colonization within natural biofilms is not a spatially random process, but rather involves strong positive interactions between communicating cells that influence their neighbors’ aggregated colonization behavior. Geostatistical analysis of the data provide statistically defendable estimates of the micrometer scale and interpolation maps of the spatial heterogeneity and local intensity at which these microbial interactions autocorrelate with their spatial patterns of distribution. Including in situ image analysis in cell communication studies fills an important gap in understanding the spatially dependent microbial ecophysiology that governs the intensity of biofilm colonization and its unique architecture. Full article
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Open AccessArticle luxS Mutant Regulation: Quorum Sensing Impairment or Methylation Disorder?
Sensors 2012, 12(5), 6176-6185; doi:10.3390/s120506176
Received: 19 March 2012 / Revised: 12 April 2012 / Accepted: 20 April 2012 / Published: 10 May 2012
Cited by 1 | PDF Full-text (436 KB) | HTML Full-text | XML Full-text
Abstract
AI-2–mediated quorum sensing has been identified in various bacteria, including both Gram-negative and Gram-positive species, and numerous phenotypes have been reported to be regulated by this mechanism, using the luxS-mutant strain. But the AI-2 production process confused this regulatory function; some considered
[...] Read more.
AI-2–mediated quorum sensing has been identified in various bacteria, including both Gram-negative and Gram-positive species, and numerous phenotypes have been reported to be regulated by this mechanism, using the luxS-mutant strain. But the AI-2 production process confused this regulatory function; some considered this regulation as the result of a metabolic change, which refers to an important metabolic cycle named activated methyl cycle (AMC), caused by luxS-mutant simultaneously with the defect of AI-2. Herein we hypothesized that the quorum sensing system—not the metabolic aspect—is responsible for such a regulatory function. In this study, we constructed plasmids infused with sahH and induced protein expression in the luxS-mutant strain to make the quorum-sensing system and metabolic system independent. The biofilm-related genes were investigated by real-time polymerase chain reaction (PCR), and the results demonstrated that the quorum-sensing completed strain restored the gene expression of the defective strain, but the metabolically completed one did not. This evidence supported our hypothesis that the autoinducer-2-mediated, quorum-sensing system, not the AMC, was responsible for luxS mutant regulation. Full article
Open AccessArticle Characterization of Quorum Sensing and Quorum Quenching Soil Bacteria Isolated from Malaysian Tropical Montane Forest
Sensors 2012, 12(4), 4846-4859; doi:10.3390/s120404846
Received: 15 March 2012 / Revised: 4 April 2012 / Accepted: 6 April 2012 / Published: 13 April 2012
Cited by 35 | PDF Full-text (348 KB) | HTML Full-text | XML Full-text
Abstract
We report the production and degradation of quorum sensing N-acyl-homoserine lactones by bacteria isolated from Malaysian montane forest soil. Phylogenetic analysis indicated that these isolates clustered closely to the genera of Arthrobacter, Bacillus and Pseudomonas. Quorum quenching activity was detected
[...] Read more.
We report the production and degradation of quorum sensing N-acyl-homoserine lactones by bacteria isolated from Malaysian montane forest soil. Phylogenetic analysis indicated that these isolates clustered closely to the genera of Arthrobacter, Bacillus and Pseudomonas. Quorum quenching activity was detected in six isolates of these three genera by using a series of bioassays and rapid resolution liquid chromatography analysis. Biosensor screening and high resolution liquid chromatography-mass spectrometry analysis revealed the production of N-dodecanoyl-L-homoserine lactone (C12-HSL) by Pseudomonas frederiksbergensis (isolate BT9). In addition to degradation of a wide range of N-acyl-homoserine lactones, Arthrobacter and Pseudomonas spp. also degraded p-coumaroyl-homoserine lactone. To the best of our knowledge, this is the first documentation of Arthrobacter and Pseudomonas spp. capable of degrading p-coumaroyl-homoserine lactone and the production of C12-HSL by P. frederiksbergensis. Full article
Open AccessArticle Spatial Heterogeneity of Autoinducer Regulation Systems
Sensors 2012, 12(4), 4156-4171; doi:10.3390/s120404156
Received: 21 February 2012 / Revised: 15 March 2012 / Accepted: 21 March 2012 / Published: 28 March 2012
Cited by 10 | PDF Full-text (326 KB) | HTML Full-text | XML Full-text
Abstract
Autoinducer signals enable coordinated behaviour of bacterial populations, a phenomenon originally described as quorum sensing. Autoinducer systems are often controlled by environmental substances as nutrients or secondary metabolites (signals) from neighbouring organisms. In cell aggregates and biofilms gradients of signals and environmental substances
[...] Read more.
Autoinducer signals enable coordinated behaviour of bacterial populations, a phenomenon originally described as quorum sensing. Autoinducer systems are often controlled by environmental substances as nutrients or secondary metabolites (signals) from neighbouring organisms. In cell aggregates and biofilms gradients of signals and environmental substances emerge. Mathematical modelling is used to analyse the functioning of the system. We find that the autoinducer regulation network generates spatially heterogeneous behaviour, up to a kind of multicellularity-like division of work, especially under nutrient-controlled conditions. A hybrid push/pull concept is proposed to explain the ecological function. The analysis allows to explain hitherto seemingly contradicting experimental findings. Full article
Open AccessArticle Inhibition of Quorum Sensing-Controlled Virulence Factor Production in Pseudomonas aeruginosa PAO1 by Ayurveda Spice Clove (Syzygium Aromaticum) Bud Extract
Sensors 2012, 12(4), 4016-4030; doi:10.3390/s120404016
Received: 16 January 2012 / Revised: 17 March 2012 / Accepted: 21 March 2012 / Published: 27 March 2012
Cited by 58 | PDF Full-text (940 KB) | HTML Full-text | XML Full-text
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.
[...] Read more.
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. Full article
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Open AccessArticle Quorum Quenching Bacillus sonorensis Isolated from Soya Sauce Fermentation Brine
Sensors 2012, 12(4), 4065-4073; doi:10.3390/s120404065
Received: 16 January 2012 / Revised: 6 March 2012 / Accepted: 22 March 2012 / Published: 27 March 2012
Cited by 15 | PDF Full-text (675 KB) | HTML Full-text | XML Full-text
Abstract
An N-acylhomoserine lactone (AHL)-degrading bacterial strain, L62, was isolated from a sample of fermentation brine of Chinese soya sauce by using rich medium agar supplemented with soya sauce (10% v/v). L62, a rod-shaped Gram positive bacterium with amylolytic activity, was phylogentically related
[...] Read more.
An N-acylhomoserine lactone (AHL)-degrading bacterial strain, L62, was isolated from a sample of fermentation brine of Chinese soya sauce by using rich medium agar supplemented with soya sauce (10% v/v). L62, a rod-shaped Gram positive bacterium with amylolytic activity, was phylogentically related to Bacillus sonorensis by 16S ribosomal DNA and rpoB sequence analyses. B. sonorensis L62 efficiently degraded N-3-oxohexanoyl homoserine lactone and N-octanoylhomoserine lactone. However, the aiiA homologue, encoding an autoinducer inactivation enzyme catalyzing the degradation of AHLs, was not detected in L62, suggesting the presence of a different AHL-degrading gene in L62. To the best of our knowledge, this is the first report of AHL-degrading B. sonorensis from soya sauce liquid state fermentation. Full article
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Open AccessArticle A Variant Quorum Sensing System in Aeromonas veronii MTCC 3249
Sensors 2012, 12(4), 3814-3830; doi:10.3390/s120403814
Received: 21 February 2012 / Revised: 17 March 2012 / Accepted: 20 March 2012 / Published: 26 March 2012
Cited by 5 | PDF Full-text (658 KB) | HTML Full-text | XML Full-text
Abstract
We have investigated the quorum sensing control in Aeromonas veronii MTCC 3249, originally isolated as A. culicicola from the midgut of Culex quinquefasciatus. Based on biosensor assays, the bacterium showed constant production of multiple acyl-homoserine lactones (AHLs) with increasing cell-density. The luxRI
[...] Read more.
We have investigated the quorum sensing control in Aeromonas veronii MTCC 3249, originally isolated as A. culicicola from the midgut of Culex quinquefasciatus. Based on biosensor assays, the bacterium showed constant production of multiple acyl-homoserine lactones (AHLs) with increasing cell-density. The luxRI gene homologs, acuR (A. culicicola transcriptional Regulator) and acuI (A. culicicola autoInducer) were successfully amplified by inverse-PCR. Sequence analysis indicated acuRI were divergent from all known quorum sensing gene homologs in Aeromonas. Two localized regions in the C-terminal autoinducer binding domain of acuR showed indels suggesting variations in autoinducer specificity. Further, only a single copy of the quorum sensing genes was detected, suggesting a tight regulation of mechanisms under its control. Chromatography and further chemical analysis identified two AHLs in the culture supernatant: 6-carboxy-HHL (homoadipyl homoserine lactone), a novel AHL, and N-tetradecanoylhomoserine lactone. The existence of a potentially variant quorum sensing system might therefore, reflect in some way the ecological strategies adopted by this bacterium in the mosquito midgut. Full article
Open AccessArticle A Pro-Drug Approach for Selective Modulation of AI-2-Mediated Bacterial Cell-to-Cell Communication
Sensors 2012, 12(3), 3762-3772; doi:10.3390/s120303762
Received: 29 December 2011 / Revised: 26 February 2012 / Accepted: 15 March 2012 / Published: 21 March 2012
Cited by 8 | PDF Full-text (665 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The universal quorum sensing autoinducer, AI-2, is utilized by several bacteria. Analogs of AI-2 have the potential to modulate bacterial behavior. Selectively quenching the communication of a few bacteria, in the presence of several others in an ecosystem, using analogs of AI-2 is
[...] Read more.
The universal quorum sensing autoinducer, AI-2, is utilized by several bacteria. Analogs of AI-2 have the potential to modulate bacterial behavior. Selectively quenching the communication of a few bacteria, in the presence of several others in an ecosystem, using analogs of AI-2 is non-trivial due to the ubiquity of AI-2 processing receptors in many bacteria that co-exist. Herein, we demonstrate that when an AI-2 analog, isobutyl DPD (which has been previously shown to be a quorum sensing, QS, quencher in both Escherichia coli and Salmonella typhimurium) is modified with ester groups, which get hydrolyzed once inside the bacterial cells, only QS in E. coli, but not in S. typhimurium, is inhibited. The origin of this differential QS inhibition could be due to differences in analog permeation of the bacterial membranes or ester hydrolysis rates. Such differences could be utilized to selectively target QS in specific bacteria amongst a consortium of other species that also use AI-2 signaling. Full article
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Open AccessArticle N-Acyl Homoserine Lactones in Diverse Pectobacterium and Dickeya Plant Pathogens: Diversity, Abundance, and Involvement in Virulence
Sensors 2012, 12(3), 3484-3497; doi:10.3390/s120303484
Received: 15 February 2012 / Revised: 2 March 2012 / Accepted: 6 March 2012 / Published: 12 March 2012
Cited by 10 | PDF Full-text (473 KB) | HTML Full-text | XML Full-text
Abstract
Soft-rot bacteria Pectobacterium and Dickeya use N-acyl homoserine lactones (NAHSLs) as diffusible signals for coordinating quorum sensing communication. The production of NAHSLs was investigated in a set of reference strains and recently-collected isolates, which belong to six species and share the ability
[...] Read more.
Soft-rot bacteria Pectobacterium and Dickeya use N-acyl homoserine lactones (NAHSLs) as diffusible signals for coordinating quorum sensing communication. The production of NAHSLs was investigated in a set of reference strains and recently-collected isolates, which belong to six species and share the ability to infect the potato host plant. All the pathogens produced different NAHSLs, among which the 3-oxo-hexanoyl- and the 3-oxo-octanoyl-L-homoserine lactones represent at least 90% of total produced NAHSL-amounts. The level of NAHSLs varied from 0.6 to 2 pg/cfu. The involvement of NAHSLs in tuber maceration was investigated by electroporating a quorum quenching vector in each of the bacterial pathogen strains. All the NAHSL-lactonase expressing strains produced a lower amount of NAHSLs as compared to those harboring the empty vector. Moreover, all except Dickeya dadantii 3937 induced a lower level of symptoms in potato tuber assay. Noticeably, aggressiveness appeared to be independent of both nature and amount of produced signals. This work highlights that quorum sensing similarly contributed to virulence in most of the tested Pectobacterium and Dickeya, even the strains had been isolated recently or during the past decades. Thus, these key regulatory-molecules appear as credible targets for developing anti-virulence strategies against these plant pathogens. Full article
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Open AccessArticle Detection, Characterization, and Biological Effect of Quorum-Sensing Signaling Molecules in Peanut-Nodulating Bradyrhizobia
Sensors 2012, 12(3), 2851-2873; doi:10.3390/s120302851
Received: 11 February 2012 / Revised: 23 February 2012 / Accepted: 23 February 2012 / Published: 1 March 2012
Cited by 14 | PDF Full-text (1205 KB) | HTML Full-text | XML Full-text
Abstract
Bacteria of the genus Bradyrhizobium are able to establish a symbiotic relationship with peanut (Arachis hypogaea) root cells and to fix atmospheric nitrogen by converting it to nitrogenous compounds. Quorum sensing (QS) is a cell-cell communication mechanism employed by a variety
[...] Read more.
Bacteria of the genus Bradyrhizobium are able to establish a symbiotic relationship with peanut (Arachis hypogaea) root cells and to fix atmospheric nitrogen by converting it to nitrogenous compounds. Quorum sensing (QS) is a cell-cell communication mechanism employed by a variety of bacterial species to coordinate behavior at a community level through regulation of gene expression. The QS process depends on bacterial production of various signaling molecules, among which the N-acylhomoserine lactones (AHLs) are most commonly used by Gram-negative bacteria. Some previous reports have shown the production of QS signaling molecules by various rhizobia, but little is known regarding mechanisms of communication among peanut-nodulating strains. The aims of this study were to identify and characterize QS signals produced by peanut-nodulating bradyrhizobial strains and to evaluate their effects on processes related to cell interaction. Detection of AHLs in 53 rhizobial strains was performed using the biosensor strains Agrobacterium tumefaciens NTL4 (pZLR4) and Chromobacterium violaceum CV026 for AHLs with long and short acyl chains, respectively. None of the strains screened were found to produce AHLs with short acyl chains, but 14 strains produced AHLs with long acyl chains. These 14 AHL-producing strains were further studied by quantification of β-galactosidase activity levels (AHL-like inducer activity) in NTL4 (pZLR4). Strains displaying moderate to high levels of AHL-like inducer activity were subjected to chemical identification of signaling molecules by high-performance liquid chromatography coupled to mass spectrometry (LC-MS/MS). For each AHL-producing strain, we found at least four different AHLs, corresponding to N-hexanoyl-DL-homoserine lactone (C6), N-(3-oxodecanoyl)-L-homoserine lactone (3OC10), N-(3-oxododecanoyl)-L-homoserine lactone (3OC12), and N-(3-oxotetradecanoyl)-L-homoserine lactone (3OC14). Biological roles of 3OC10, 3OC12, and 3OC14 AHLs were evaluated in both AHL-producing and -non-producing peanut-nodulating strains. Bacterial processes related to survival and nodulation, including motility, biofilm formation, and cell aggregation, were affected or modified by the exogenous addition of increasing concentrations of synthetic AHLs. Our results clearly demonstrate the existence of cell communication mechanisms among bradyrhizobial strains symbiotic of peanut. AHLs with long acyl chains appear to be signaling molecules regulating important QS physiological processes in these bacteria. Full article

Review

Jump to: Research

Open AccessReview Detection of AI-2 Receptors in Genomes of Enterobacteriaceae Suggests a Role of Type-2 Quorum Sensing in Closed Ecosystems
Sensors 2012, 12(5), 6645-6665; doi:10.3390/s120506645
Received: 31 March 2012 / Revised: 11 May 2012 / Accepted: 16 May 2012 / Published: 21 May 2012
Cited by 12 | PDF Full-text (339 KB) | HTML Full-text | XML Full-text
Abstract
The LuxS enzyme, an S-ribosyl-homocysteine lyase, catalyzes the production of the signal precursor for autoinducer-2 mediated quorum sensing (QS-2) in Vibrio. Its widespread occurrence among bacteria is often considered the evidence for a universal language for interspecies communication. Presence of the luxS
[...] Read more.
The LuxS enzyme, an S-ribosyl-homocysteine lyase, catalyzes the production of the signal precursor for autoinducer-2 mediated quorum sensing (QS-2) in Vibrio. Its widespread occurrence among bacteria is often considered the evidence for a universal language for interspecies communication. Presence of the luxS gene and production of the autoinducer-2 (AI-2) signal have repeatedly been the only evidences presented to assign a functional QS-2 to the most diverse species. In fact, LuxS has a primary metabolic role as part of the activated methyl cycle. In this review we have analyzed the distribution of QS-2 related genes in Enterobacteriaceae by moving the focus of the investigation from AI-2 production to the detection of potential AI-2 receptors. The latter are common in pathogens or endosymbionts of animals, but were also found in a limited number of Enterobacteriaceae of the genera Enterobacter, Klebsiella, and Pantoea that live in close association with plants or fungi. Although a precise function of QS-2 in these species has not been identified, they all show an endophytic or endosymbiontic lifestyle that suggests a role of type-2 quorum sensing in the adaptation to closed ecosystems. Full article
Open AccessReview Classifying the Topology of AHL-Driven Quorum Sensing Circuits in Proteobacterial Genomes
Sensors 2012, 12(5), 5432-5444; doi:10.3390/s120505432
Received: 1 February 2012 / Revised: 24 March 2012 / Accepted: 26 April 2012 / Published: 27 April 2012
Cited by 10 | PDF Full-text (271 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Virulence and adaptability of many Gram-negative bacterial species are associated with an N-acylhomoserine lactone (AHL) gene regulation mechanism called quorum sensing (QS). The arrangement of quorum sensing genes is variable throughout bacterial genomes, although there are unifying themes that are common among
[...] Read more.
Virulence and adaptability of many Gram-negative bacterial species are associated with an N-acylhomoserine lactone (AHL) gene regulation mechanism called quorum sensing (QS). The arrangement of quorum sensing genes is variable throughout bacterial genomes, although there are unifying themes that are common among the various topological arrangements. A bioinformatics survey of 1,403 complete bacterial genomes revealed characteristic gene topologies in 152 genomes that could be classified into 16 topological groups. We developed a concise notation for the patterns and show that the sequences of LuxR regulators and LuxI autoinducer synthase proteins cluster according to the topological patterns. The annotated topologies are deposited online with links to sequences and genome annotations at http://bacteria.itk.ppke.hu/QStopologies/. Full article
Open AccessReview Quorum Quenching Revisited—From Signal Decays to Signalling Confusion
Sensors 2012, 12(4), 4661-4696; doi:10.3390/s120404661
Received: 28 February 2012 / Revised: 23 March 2012 / Accepted: 26 March 2012 / Published: 10 April 2012
Cited by 58 | PDF Full-text (344 KB) | HTML Full-text | XML Full-text
Abstract
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
[...] Read more.
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. Full article
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Open AccessReview Quorum Sensing and Expression of Virulence in Pectobacteria
Sensors 2012, 12(3), 3327-3349; doi:10.3390/s120303327
Received: 16 January 2012 / Revised: 21 February 2012 / Accepted: 2 March 2012 / Published: 8 March 2012
Cited by 18 | PDF Full-text (285 KB) | HTML Full-text | XML Full-text
Abstract
Quorum sensing (QS) is a population density-dependent regulatory mechanism in which gene expression is coupled to the accumulation of a chemical signaling molecule. QS systems are widespread among the plant soft-rotting bacteria. In Pectobacterium carotovorum, at least two QS systems exist being
[...] Read more.
Quorum sensing (QS) is a population density-dependent regulatory mechanism in which gene expression is coupled to the accumulation of a chemical signaling molecule. QS systems are widespread among the plant soft-rotting bacteria. In Pectobacterium carotovorum, at least two QS systems exist being specified by the nature of chemical signals involved. QS in Pectobacterium carotovorum uses N-acylhomoserine lactone (AHL) based, as well as autoinducer-2 (AI-2) dependent signaling systems. This review will address the importance of the QS in production of virulence factors and interaction of QS with other regulatory systems in Pectobacterium carotovorum. Full article
Open AccessReview α-Hydroxyketone Synthesis and Sensing by Legionella and Vibrio
Sensors 2012, 12(3), 2899-2919; doi:10.3390/s120302899
Received: 16 January 2012 / Revised: 23 February 2012 / Accepted: 23 February 2012 / Published: 2 March 2012
Cited by 12 | PDF Full-text (866 KB) | HTML Full-text | XML Full-text
Abstract
Bacteria synthesize and sense low molecular weight signaling molecules, termed autoinducers, to measure their population density and community complexity. One class of autoinducers, the α-hydroxyketones (AHKs), is produced and detected by the water-borne opportunistic pathogens Legionella pneumophila and Vibrio cholerae, which cause
[...] Read more.
Bacteria synthesize and sense low molecular weight signaling molecules, termed autoinducers, to measure their population density and community complexity. One class of autoinducers, the α-hydroxyketones (AHKs), is produced and detected by the water-borne opportunistic pathogens Legionella pneumophila and Vibrio cholerae, which cause Legionnaires’ disease and cholera, respectively. The “Legionella quorum sensing” (lqs) or “cholera quorum sensing” (cqs) genes encode enzymes that produce and sense the AHK molecules “Legionella autoinducer-1” (LAI-1; 3-hydroxypentadecane-4-one) or cholera autoinducer-1 (CAI-1; 3-hydroxytridecane-4-one). AHK signaling regulates the virulence of L. pneumophila and V. cholerae, pathogen-host cell interactions, formation of biofilms or extracellular filaments, expression of a genomic “fitness island” and competence. Here, we outline the processes, wherein AHK signaling plays a role, and review recent insights into the function of proteins encoded by the lqs and cqs gene clusters. To this end, we will focus on the autoinducer synthases catalysing the biosynthesis of AHKs, on the cognate trans-membrane sensor kinases detecting the signals, and on components of the down-stream phosphorelay cascade that promote the transmission and integration of signaling events regulating gene expression. Full article
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Open AccessReview Quorum Sensing and Bacterial Social Interactions in Biofilms
Sensors 2012, 12(3), 2519-2538; doi:10.3390/s120302519
Received: 6 January 2012 / Revised: 9 February 2012 / Accepted: 10 February 2012 / Published: 23 February 2012
Cited by 80 | PDF Full-text (256 KB) | HTML Full-text | XML Full-text
Abstract
Many bacteria are known to regulate their cooperative activities and physiological processes through a mechanism called quorum sensing (QS), in which bacterial cells communicate with each other by releasing, sensing and responding to small diffusible signal molecules. The ability of bacteria to communicate
[...] Read more.
Many bacteria are known to regulate their cooperative activities and physiological processes through a mechanism called quorum sensing (QS), in which bacterial cells communicate with each other by releasing, sensing and responding to small diffusible signal molecules. The ability of bacteria to communicate and behave as a group for social interactions like a multi-cellular organism has provided significant benefits to bacteria in host colonization, formation of biofilms, defense against competitors, and adaptation to changing environments. Importantly, many QS-controlled activities have been involved in the virulence and pathogenic potential of bacteria. Therefore, understanding the molecular details of quorum sensing mechanisms and their controlled social activities may open a new avenue for controlling bacterial infections. Full article

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