scholarly journals Quorum-Sensing System and Stationary-Phase Sigma Factor (rpoS) of the Onion Pathogen Burkholderia cepacia Genomovar I Type Strain, ATCC 25416

2003 ◽  
Vol 69 (3) ◽  
pp. 1739-1747 ◽  
Author(s):  
Claudio Aguilar ◽  
Iris Bertani ◽  
Vittorio Venturi
Keyword(s):  
Quorum Sensing ◽  
Stationary Phase ◽  
Sigma Factor ◽  
Burkholderia Cepacia ◽  
Type Strain ◽  
Plant Pathogens ◽  
Signal Molecules ◽  
Strain Atcc ◽  
Sensing System ◽  
Quorum Sensing System

ABSTRACT Bacterial strains belonging to Burkholderia cepacia can be human opportunistic pathogens, plant pathogens, and plant growth promoting and have remarkable catabolic activity. B. cepacia consists of several genomovars comprising what is now known as the B. cepacia complex. Here we report the quorum-sensing system of a genomovar I onion rot type strain ATCC 25416. Quorum sensing is a cell-density-dependent regulatory response which involves the production of N-acyl homoserine lactone (HSL) signal molecules. The cep locus has been inactivated in the chromosome, and it has been shown that CepI is responsible for the biosynthesis of an N-hexanoyl HSL (C6-HSL) and an N-octanoyl HSL (C8-HSL) and that the cep locus regulates protease production as well as onion pathogenicity via the expression of a secreted polygalacturonase. A cep-lacZ-based sensor plasmid has been constructed and used to demonstrate that CepR responded to C6-HSL with only 15% of the molar efficiency of C8-HSL, that a cepR knockout mutant synthesized 70% less HSLs, and that CepR responded best towards long-chain HSLs. In addition, we also report the cloning and characterization of the stationary-phase sigma factor gene rpoS of B. cepacia ATCC 25416. It was established that quorum sensing in B. cepacia has a negative effect on rpoS expression as determined by using an rpoS-lacZ transcriptional fusion; on the other hand, rpoS-null mutants displayed no difference in the accumulation of HSL signal molecules.

scholarly journals Inactivation of traP Has No Effect on the Agr Quorum-Sensing System or Virulence of Staphylococcus aureus

2007 ◽  
Vol 75 (9) ◽  
pp. 4519-4527 ◽  
Author(s):  
Lindsey N. Shaw ◽  
Ing-Marie Jonsson ◽  
Vineet K. Singh ◽  
Andrej Tarkowski ◽  
George C. Stewart
Keyword(s):  
Staphylococcus Aureus ◽  
Quorum Sensing ◽  
Type Strain ◽  
Wild Type Strain ◽  
Surface Proteins ◽  
Virulence Determinants ◽  
Wild Type ◽  
Expression Levels ◽  
Sensing System ◽  
Quorum Sensing System

ABSTRACT The success of Staphylococcus aureus as a pathogen can largely be attributed to the plethora of genetic regulators encoded within its genome that temporally regulate its arsenal of virulence determinants throughout its virulence lifestyle. Arguably the most important of these is the two-component, quorum-sensing system agr. Over the last decade, the controversial presence of a second quorum-sensing system (the TRAP system) has been proposed, and it has been mooted to function as the master regulator of virulence in S. aureus by modulating agr. Mutants defective in TRAP are reported to be devoid of agr expression, lacking in hemolytic activity, essentially deficient in the secretion of virulence determinants, and avirulent in infection models. A number of research groups have questioned the validity of the TRAP findings in recent years; however, a thorough and independent analysis of its role in S. aureus physiology and pathogenesis has not been forthcoming. Therefore, we have undertaken such an analysis of the TRAP locus of S. aureus. We found that a traP mutant was equally hemolytic as the wild-type strain. Furthermore, transcriptional profiling found no alterations in the traP mutant in expression levels of agr or in expression levels of multiple agr-regulated genes (hla, sspA, and spa). Analysis of secreted and surface proteins of the traP mutant revealed no deviation in comparison to the parent. Finally, analysis conducted using a murine model of S. aureus septic arthritis revealed that, in contrast to an agr mutant, the traP mutant was just as virulent as the wild-type strain.

scholarly journals Quorum Sensing Regulates Denitrification in Pseudomonas aeruginosa PAO1

2007 ◽  
Vol 189 (13) ◽  
pp. 4969-4972 ◽  
Author(s):  
Masanori Toyofuku ◽  
Nobuhiko Nomura ◽  
Tatsuya Fujii ◽  
Naoki Takaya ◽  
Hideaki Maseda ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Homoserine Lactone ◽  
Anaerobic Growth ◽  
Signal Molecules ◽  
Pseudomonas Aeruginosa Pao1 ◽  
Sensing System ◽  
Quorum Sensing System ◽  
Denitrification Activity

ABSTRACT Anaerobic growth of Pseudomonas aeruginosa PAO1 was affected by quorum sensing. Deletion of genes that produce N-acyl-l-homoserine lactone signals resulted in an increase in denitrification activity, which was repressed by exogenous signal molecules. The effect of the las quorum-sensing system was dependent on the rhl quorum-sensing system in regulating denitrification.

scholarly journals Killing of Caenorhabditis elegans by Burkholderia cepacia is controlled by the cep quorum-sensing system

2003 ◽  
Vol 5 (5) ◽  
pp. 343-351 ◽  
Author(s):  
Manuela Kothe ◽  
Melanie Antl ◽  
Birgit Huber ◽  
Kilian Stoecker ◽  
Doreen Ebrecht ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Quorum Sensing ◽  
Burkholderia Cepacia ◽  
Sensing System ◽  
Quorum Sensing System

scholarly journals Pseudomonas aeruginosa Virulence Analyzed in a Dictyostelium discoideum Host System

2002 ◽  
Vol 184 (11) ◽  
pp. 3027-3033 ◽  
Author(s):  
Pierre Cosson ◽  
Laurence Zulianello ◽  
Olivier Join-Lambert ◽  
François Faurisson ◽  
Leigh Gebbie ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Type Strain ◽  
Wild Type Strain ◽  
Model System ◽  
Wild Type ◽  
Strain Pao1 ◽  
Antibiotic Resistant ◽  
Sensing System ◽  
Quorum Sensing System ◽  
Simple Model System

ABSTRACT Pseudomonas aeruginosa is an important opportunistic pathogen that produces a variety of cell-associated and secreted virulence factors. P. aeruginosa infections are difficult to treat effectively because of the rapid emergence of antibiotic-resistant strains. In this study, we analyzed whether the amoeba Dictyostelium discoideum can be used as a simple model system to analyze the virulence of P. aeruginosa strains. The virulent wild-type strain PAO1 was shown to inhibit growth of D. discoideum. Isogenic mutants deficient in the las quorum-sensing system were almost as inhibitory as the wild type, while rhl quorum-sensing mutants permitted growth of Dictyostelium cells. Therefore, in this model system, factors controlled by the rhl quorum-sensing system were found to play a central role. Among these, rhamnolipids secreted by the wild-type strain PAO1 could induce fast lysis of D. discoideum cells. By using this simple model system, we predicted that certain antibiotic-resistant mutants of P. aeruginosa should show reduced virulence. This result was confirmed in a rat model of acute pneumonia. Thus, D. discoideum could be used as a simple nonmammalian host system to assess pathogenicity of P. aeruginosa.

scholarly journals The cep quorum-sensing system of Burkholderia cepacia H111 controls biofilm formation and swarming motility

Microbiology ◽  
2001 ◽  
Vol 147 (9) ◽  
pp. 2517-2528 ◽  
Author(s):  
Birgit Huber ◽  
Kathrin Riedel ◽  
Morten Hentzer ◽  
Arne Heydorn ◽  
Astrid Gotschlich ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Biofilm Formation ◽  
Burkholderia Cepacia ◽  
Swarming Motility ◽  
Sensing System ◽  
Quorum Sensing System

scholarly journals Identification and Characterization of a GDSL Esterase Gene Located Proximal to the swr Quorum-Sensing System of Serratia liquefaciens MG1

2003 ◽  
Vol 69 (7) ◽  
pp. 3901-3910 ◽  
Author(s):  
Kathrin Riedel ◽  
Daniela Talker-Huiber ◽  
Michael Givskov ◽  
Helmut Schwab ◽  
Leo Eberl
Keyword(s):  
Quorum Sensing ◽  
Extracellular Enzymes ◽  
Tween 80 ◽  
Homoserine Lactone ◽  
Growth Conditions ◽  
Tween 20 ◽  
Signal Molecules ◽  
Sensing System ◽  
Serratia Liquefaciens ◽  
Quorum Sensing System

ABSTRACT Serratia liquefaciens MG1 employs the swr quorum-sensing system to control various functions, including production of extracellular enzymes and swarming motility. Here we report the sequencing of the swr flanking DNA regions. We identified a gene upstream of swrR and transcribed in the same direction, designated estA, which encodes an esterase that belongs to family II of lipolytic enzymes. EstA was heterologously expressed in Escherichia coli, and the substrate specificity of the enzyme was determined in crude extracts. With the aid of zymograms visualizing EstA on polyacrylamide gels and by the analysis of a transcriptional fusion of the estA promoter to the promoterless luxAB genes, we showed that expression of the esterase is not regulated by the swr quorum-sensing system. An estA mutant was generated and was found to exhibit growth defects on minimal medium containing Tween 20 or Tween 80 as the sole carbon source. Moreover, we show that the mutant produces greatly reduced amounts of N-acyl-homoserine lactone (AHL) signal molecules on Tween-containing medium compared with the wild type, suggesting that under certain growth conditions EstA may be important for providing the cell with precursors required for AHL biosynthesis.

scholarly journals Identification and Characterization of an N-Acylhomoserine Lactone-Dependent Quorum-Sensing System in Pseudomonas putida Strain IsoF

2002 ◽  
Vol 68 (12) ◽  
pp. 6371-6382 ◽  
Author(s):  
Anette Steidle ◽  
Marie Allesen-Holm ◽  
Kathrin Riedel ◽  
Gabriele Berg ◽  
Michael Givskov ◽  
...  
Keyword(s):  
Amino Acid ◽  
Quorum Sensing ◽  
Pseudomonas Putida ◽  
Gene Cluster ◽  
Intergenic Region ◽  
Phenotypic Traits ◽  
Signal Molecules ◽  
Structural Development ◽  
Sensing System ◽  
Quorum Sensing System

ABSTRACT Recent reports have shown that several strains of Pseudomonas putida produce N-acylhomoserine lactones (AHLs). These signal molecules enable bacteria to coordinately express certain phenotypic traits in a density-dependent manner in a process referred to as quorum sensing. In this study we have cloned a genomic region of the plant growth-promoting P. putida strain IsoF that, when present in trans, provoked induction of a bioluminescent AHL reporter plasmid. Sequence analysis identified a gene cluster consisting of four genes: ppuI and ppuR, whose predicted amino acid sequences are highly similar to proteins of the LuxI-LuxR family, an open reading frame (ORF) located in the intergenic region between ppuI and ppuR with significant homology to rsaL from Pseudomonas aeruginosa, and a gene, designated ppuA, present upstream of ppuR, the deduced amino acid sequence of which shows similarity to long-chain fatty acid coenzyme A ligases from various organisms. Using a transcriptional ppuA::luxAB fusion we demonstrate that expression of ppuA is AHL dependent. Furthermore, transcription of the AHL synthase ppuI is shown to be subject to quorum-sensing regulation, creating a positive feedback loop. Sequencing of the DNA regions flanking the ppu gene cluster indicated that the four genes form an island in the suhB-PA3819 intergenic region of the currently sequenced P. putida strain KT2440. Moreover, we provide evidence that the ppu genes are not present in other AHL-producing P. putida strains, indicating that this gene cluster is so far unique for strain IsoF. While the wild-type strain formed very homogenous biofilms, both a ppuI and a ppuA mutant formed structured biofilms with characteristic microcolonies and water-filled channels. These results suggest that the quorum-sensing system influences biofilm structural development.

scholarly journals The hanR/hanI quorum-sensing system of Halomonas anticariensis, a moderately halophilic bacterium

Microbiology ◽  
2011 ◽  
Vol 157 (12) ◽  
pp. 3378-3387 ◽  
Author(s):  
Ali Tahrioui ◽  
Emilia Quesada ◽  
Inmaculada Llamas
Keyword(s):  
Quorum Sensing ◽  
Halophilic Bacterium ◽  
Transcriptional Analysis ◽  
Signal Molecules ◽  
Rt Pcr ◽  
Significant Group ◽  
Signalling Molecules ◽  
Sensing System ◽  
Moderately Halophilic Bacterium ◽  
Quorum Sensing System

Quorum sensing is a cell density-dependent gene expression mechanism found in many Gram-negative bacteria which involves the production of signal molecules such as N-acylhomoserine lactones (AHLs). One significant group of micro-organisms in which quorum sensing has not been previously studied, however, are the moderate halophiles. We describe here the results of our studies of the quorum-sensing system in Halomonas anticariensis FP35T, which is composed of luxR/luxI homologues: hanR (the putative transcriptional regulator gene) and hanI (the autoinducer synthase gene). To understand how the hanR/hanI system is organized and regulated we conducted RT-PCR and quantitative real-time PCR assays. Transcriptional analysis indicated that the hanR and hanI genes are on the same transcript and that their transcription is growth phase-dependent. HanI seems to be the only autoinducer synthase responsible for the synthesis of AHLs by the bacterium, since the inactivation of hanI resulted in the complete loss of its AHLs. We also found that the hanI gene appears to be transcribed from its own promoter and that its expression does not depend upon HanR. This finding was supported by the fact that the FP35hanR mutant showed AHL-producing activity and hanI expression similar to that of the wild-type strain, the latter being measured by RT-PCR. Moreover, hanR is expressed from its own promoter and appears to be independent of the AHL signalling molecules produced by HanI.

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