Microarray Analysis of Pseudomonas aeruginosa Quorum-Sensing Regulons: Effects of Growth Phase and Environment

Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, New York 14642, USA.
Journal of Bacteriology (Impact Factor: 2.81). 04/2003; 185(7):2080-95. DOI: 10.1128/JB.185.7.2080-2095.2003
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Bacterial communication via quorum sensing (QS) has been reported to be important in the production of virulence factors,
antibiotic sensitivity, and biofilm development. Two QS systems, known as the las and rhl systems, have been identified previously in the opportunistic pathogen Pseudomonas aeruginosa. High-density oligonucleotide microarrays for the P. aeruginosa PAO1 genome were used to investigate global gene expression patterns modulated by QS regulons. In the initial experiments
we focused on identifying las and/or rhl QS-regulated genes using a QS signal generation-deficient mutant (PAO-JP2) that was cultured with and without added exogenous
autoinducers [N-(3-oxododecanoyl) homoserine lactone and N-butyryl homoserine lactone]. Conservatively, 616 genes showed statistically significant differential expression (P ≤ 0.05) in response to the exogenous autoinducers and were classified as QS regulated. A total of 244 genes were identified
as being QS regulated at the mid-logarithmic phase, and 450 genes were identified as being QS regulated at the early stationary
phase. Most of the previously reported QS-promoted genes were confirmed, and a large number of additional QS-promoted genes
were identified. Importantly, 222 genes were identified as being QS repressed. Environmental factors, such as medium composition
and oxygen availability, eliminated detection of transcripts of many genes that were identified as being QS regulated.

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Available from: Victoria E Wagner, Feb 11, 2015
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    • "It is known that the bacterial environment (i.e. culture conditions) has an important effect on the expression and the detection of QSregulated genes, these genes being either upregulated or downregulated (Makemson et al., 1997; Wagner et al., 2003). Indeed, QS is connected to other regulatory networks , such as the cyclic di-GMP signalling system, with the overall goal of allowing bacteria to adapt and respond to changing environmental conditions, at low or high cell density (Srivastava & Waters, 2012). "
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    ABSTRACT: Various phenotypes ranging from biofilm formation to pigment production have been shown to be regulated by Quorum Sensing in many bacteria. However, studies of the regulation of pigments produced by marine bacteria in saline conditions and of biofilm-associated phenotypes are scarcer. This study focuses on the demonstration of the existence of a QS communication system involving N-acylhomoserine lactones (AHLs) in the Mediterranean Sea strain Pseudoalteromonas ulvae TC14. We have investigated whether TC14 produces the violacein pigment and if intrinsic or exogenous AHLs could influence its production and modulate biofilm-associated phenotypes. Here, we demonstrate that the purple pigment produced by TC14 is violacein. The study shows that in planktonic conditions, TC14 produces more pigment in the medium in which it grows less. Using different approaches, the results also show that TC14 does not produce intrinsic AHLs in our conditions. When exogenous AHLs is added in planktonic conditions, the production of violacein is up-regulated by C6-, C12-, 3-oxo-C8, 3-oxo-C12-HSLs and down-regulated by 3-oxo-C6-HSL. In sessile conditions, 3-oxo-C8-HSL up-regulates the production of violacein. The study of the biofilm-associated phenotypes shows that oxo-derivated-HSLs decrease adhesion, swimming and biofilm formation. While 3-oxo-C8 and 3-oxo-C12-HSLs decrease both swimming and adhesion, 3-oxo-C6-HSLs not only decreases violacein production in planktonic conditions but also swimming, adhesion and more subtly biofilm formation. Therefore, TC14 may possess a functional LuxR- type QS receptor capable of sensing extrinsic AHLs, which control violacein production, motility, adhesion and biofilm formation.
    Microbiology 08/2015; 161(10). DOI:10.1099/mic.0.000147 · 2.56 Impact Factor
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    • "). QS-controlled genes can constitute around 10 % of the bacterial genome (Wagner et al. 2003). QS systems play a very important role during the development and dispersal of bacterial biofilms. "
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    ABSTRACT: Nearly all bacterial species, including pathogens, have the ability to form biofilms. Biofilms are defined as structured ecosystems in which microbes are attached to surfaces and embedded in a matrix composed of polysaccharides, eDNA, and proteins, and their development is a multistep process. Bacterial biofilms constitute a large medical problem due to their extremely high resistance to various types of therapeutics, including conventional antibiotics. Several environmental and genetic signals control every step of biofilm development and dispersal. From among the latter, quorum sensing, cyclic diguanosine-5'-monophosphate, and small RNAs are considered as the main regulators. The present review describes the control role of these three regulators in the life cycles of biofilms built by Pseudomonas aeruginosa, Staphylococcus aureus, Salmonella enterica serovar Typhimurium, and Vibrio cholerae. The interconnections between their activities are shown. Compounds and strategies which target the activity of these regulators, mainly quorum sensing inhibitors, and their potential role in therapy are also assessed.
    Journal of applied genetics 08/2015; DOI:10.1007/s13353-015-0309-2 · 1.48 Impact Factor
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    • "Similar observations have been reported in several studies, where the efficient performance of the QS system was observed under high cell densities, represented by higher levels of AHL in Photobacterium fischeri and Ps. aeruginosa (Nealson et al., 1970; Wagner et al., 2003). However, neither of the Pectobacterium spp. "
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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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