Article

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: 2.69). 04/2003; 185(7):2080-95. DOI: 10.1128/JB.185.7.2080-2095.2003
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ABSTRACT 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; DOI:10.1099/mic.0.000147 · 2.84 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.
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    • "Quorum sensing network consist of mainly three interdependent systems, the lasI–lasR, rhlI–rhlR [17] and Pqs systems [18]. lasI–lasR system regulate the production of N-(3-oxododecanoyl) homoserine lactone (3O-C12-HSL) and rhlI–rhlR system regulate the production of N-butyryl homoserine lactone (C4-HSL) [19]. Pqs signaling system produce 2-heptyl-3-hydroxy-4-quinolone (PQS) molecule that plays an interconnecting role in quorum sensing hierarchy of P. aeruginosa between las and rhl systems [18]. "
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