title: Regulation of las and rhl quorum sensing in Pseudomonas aeruginosa.
abstract: The production of several virulence factors by Pseudomonas aeruginosa is controlled according to cell density through two quorum-sensing systems, las and rhl. The las system is comprised of the transcriptional activator protein LasR and of LasI, which directs the synthesis of the autoinducer PAI-1. Similarly, the rhl system consists of the transcriptional activator protein RhlR and of RhlI, which directs synthesis of the autoinducer PAI-2 (formerly referred to as factor 2). To study the interrelation between the two P. aeruginosa quorum-sensing systems, we fused a lacZ reporter gene to lasR, rhlR, and rhlA and monitored expression of these three genes under various conditions. Our data indicate that lasR and rhlR are expressed in a growth-dependent manner, with activation of each gene occurring during the last half of log-phase growth. We also show that the las quorum-sensing system controls the rhl quorum-sensing system in two ways. First, we found that LasR and PAI-1 activated rhlR transcription. Second, we showed that PAI-1 blocked PAI-2 from binding to RhlR, thereby inhibiting the expression of rhlA. Our data thus indicate that the las system exerts two levels of control on RhlR, transcriptional and posttranslational.
authors.affiliation: Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, New York 14642, USA.
authors.forename: E C
authors.initials: EC
authors.lastname: Pesci
authors.forename: J P
authors.initials: JP
authors.lastname: Pearson
authors.forename: P C
authors.initials: PC
authors.lastname: Seed
authors.forename: B H
authors.initials: BH
authors.lastname: Iglewski
mesh_terms: D015107:4-Butyrolactone / Q000031:analogs & derivatives / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000494:pharmacology; D005798:Genes, Bacterial / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000235:genetics* / Q000254:growth & development; D015534:Trans-Activators / Q000235:genetics* / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C080365:LasR protein, Pseudomonas aeruginosa; C092312:N-butyrylhomoserine lactone; D015534:Trans-Activators; D015107:4-Butyrolactone