A novel two-component system BqsS-BqsR modulates quorum sensing-dependent biofilm decay inPseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa can grow either as planktonic- or biofilm-form in response to environmental changes. Recent studies show that switching from biofilm to planktonic lifestyle requires rhamnolipids. Here we report the identification of a novel twocomponent system BqsS-BqsR that regulates biofilm decay in P. aeruginosa. BqsS is a multidomain sensor kinase and BqsR is an OmpR-like response regulator. Deletion of either bqsS or bqsR in P. aeruginosa mPAO1 resulted in a significant increase in biofilm formation. Time course analysis showed that the bqsS-bqsR mutants were defective in biofilm dispersal and in rhamnolipid production. Mutation of the BqsS-BqsR two-component system did not affect the biosynthesis of long chain quorum sensing (QS) signal N-3-oxo-dodecanoyl-homoserine lactone (3OC12HSL) but resulted in reduced production of the short chain QS signal N-butyryl-L-homoserine lactone (C4HSL) and the Pseudomonas quinolone signal (PQS). Exogenous addition of C4HSL, PQS or rhamnolipids to the bqsS mutant reduced the biofilm formation to the wild-type level. Evidence suggests that the BqsS-BqsR two-component system might promote conversion of anthranilate to PQS. Taken together, these results establish BqsS-BqsR as a novel two-component system that regulates biofilm decay in P. aeruginosa by modulating biosynthesis of QS signals and rhamnolipids.

BqsR/BqsS Constitute a Two-Component System That Senses Extracellular Fe(II) in Pseudomonas aeruginosa

“…All of the genes from PA14_29710 to PA14_ 29750 appear to be transcriptionally connected (Fig. 1), and thus we refer to this operon as the bqsPQRST operon, because homologs of BqsS and BqsR (exhibiting 100% amino acid identity) were previously identified in P. aeruginosa strain PAO1 for their role in biofilm development and quorum sensing (13). Whether bqsT is a bona fide member of this operon is less clear, as qRT-PCR results (see Fig.…”

“…BqsR/ BqsS autoregulates its own expression, is turned on by Fe(II) concentrations of Ͼ10 M, and does not respond to other physiologically relevant dipositive ions. Previously, BqsR/BqsS was shown to play a role in the dispersal of P. aeruginosa strain PAO1 biofilms (13). This appears to be due to the fact that biofilms lacking BqsR or BqsS produce lower concentrations of rhamnolipids, which are known to promote biofilm dispersal (7).…”

Biofilm Dispersal: Mechanisms, Clinical Implications, and Potential Therapeutic Uses

“…In P. aeruginosa, biofilms formed by mutant strains deficient in the production of C4-HSL (ΔlasI/rhlI) do not undergo central hollowing (Purevdorj-Gage et al, 2005), and the addition of exogenous C4-HSL to wild-type biofilms induces biofilm dispersal (Schooling et al, 2004;Dong et al, 2008). C4-HSL may induce dispersal by up-regulation of the rhamnolipid biosynthetic gene rhaA (Davey et al, 2003).…”

“…4F) (Pesci et al, 1999). It has been shown (Dong et al, 2008) that exogenous PQS induces dispersal of wild-type P. aeruginosa biofilms cultured in microplate wells. Previous studies showed that PQS mediates cell death and DNA release in P. aeruginosa biofilms (Allesen-Holm et al, 2006), which suggests that PQS may induce central hollowing.…”

Aseptic Loosening of Total Hip Arthroplasty: Infection Always Should be Ruled Out

“…Biofilm is a complex structure comprising microorganisms enveloped in macromolecules of glycocalyx and other protective films [7,16]. Recent discoveries indicate that microorganisms in the biofilm communicate using sophisticated molecular signaling mechanisms that allow them to determine the optimal time to become planktonic [13,26,28]. Because isolation of a pathogen from the fluid or tissue around an infected joint mostly relies on detecting planktonic organisms, cases of culturenegative infection occur.…”