Bacteria use a cell-cell communication system termed quorum-sensing (QS) to adjust population size by coordinating the costly but beneficial cooperative behaviors. It has long been suggested that bacterial social conflict for expensive extracellular products may drive QS divergence and cause the "tragedy of the commons". However, the underlying molecular mechanism of social divergence and its e...

Microbes are subjected to selective pressures during chronic infections of host tissues. Pseudomonas aeruginosa isolates with inactivating mutations in the transcriptional regulator LasR are frequently selected within the airways of people with cystic fibrosis (CF), and infection with these isolates has been associated with poorer lung function outcomes. The mechanisms underlying selection for ...

The opportunistic pathogen Pseudomonas aeruginosa undergoes genetic change during chronic airway infection of cystic fibrosis (CF) patients. One common change is a mutation inactivating lasR, which encodes a transcriptional regulator that responds to a homoserine lactone signal to activate expression of acute virulence factors. Colonies of lasR mutants visibly accumulated the iridescent interce...

The enzyme elastase is an important virulence factor of the opportunistic human pathogen Pseudomonas aeruginosa. Previous studies have shown that expression of the P. aeruginosa elastase gene (lasB) requires both an activator protein, LasR, and an N-acylhomoserine lactone compound termed Pseudomonas autoinducer (PAI). In this study, we analyzed the lasB promoter region to learn more about lasB ...

Two quorum-sensing systems (las and rhl) regulate virulence gene expression in Pseudomonas aeruginosa. The las system consists of a transcriptional activator, LasR, and LasI, which directs the synthesis of the autoinducer N-(3-oxododecanoyl) homoserine lactone (PAI-1). Induction of lasB (encoding elastase) and other virulence genes requires LasR and PAI-1. The rhl system consists of a putative ...

Many common bacterial pathogens utilize quorum sensing to coordinate group behaviors and initiate virulence at high cell densities. The use of small molecules to block quorum sensing provides a means of abrogating pathogenic phenotypes, but many known quorum sensing modulators have limitations, including hydrolytic instability and displaying non-monotonic dose curves (indicative of additional t...

b a ckground: quorum-sensing systems regulate expression of several virulence factors in pseudomonas aeruginosa . this study investigated the relation between expression of the las quorum-sensing system and expression of mexy and ampc in35 clinical isolates of p. aeruginosa . m e t hods: antibiotic susceptibility was determined by the disc diffusion method according to the clinical and laborato...

Many Proteobacteria govern responses to changes in cell density by using acyl-homoserine lactone (AHL) quorum-sensing (QS) signaling. Similar to the LuxI-LuxR system described in Vibrio fischeri, a minimal AHL QS circuit comprises a pair of genes, a luxI-type synthase gene encoding an enzyme that synthesizes an AHL and a luxR-type AHL-responsive transcription regulator gene. In most bacteria th...

Candida albicans has been previously shown to stimulate the production of Pseudomonas aeruginosa phenazine toxins in dual-species colony biofilms. Here, we report that P. aeruginosa lasR mutants, which lack the master quorum sensing system regulator, regain the ability to produce quorum-sensing-regulated phenazines when cultured with C. albicans. Farnesol, a signalling molecule produced by C. a...

Along with their cognate acyl-homoserine lactone signals, the quorum sensing regulators LasR and RhlR control the expression of hundreds of genes in the opportunistic human pathogen Pseudomonas aeruginosa. This extensive, overlapping regulatory network affords the opportunity to systematically investigate the sequence requirements and specificity determinants of large families of target promote...