Global regulation in Pseudomonas aeruginosa: the regulatory protein AlgR2 (AlgQ) acts as a modulator of quorum sensing.

The Pseudomonas aeruginosa protein AlgR2 (AlgQ) was originally identified as a regulatory protein implicated in alginate production. It also regulates the synthesis of polyphosphate as well as of a variety of secretable virulence factors, upregulating neuraminidase and siderophore synthesis and downregulating rhamnolipid biosurfactant and extracellular protease synthesis. In this study, we show that the regulatory effect of AlgR2 on elastase protease synthesis is exerted at transcriptional level on the lasB gene. We also demonstrate that AlgR2 negatively modulates the expression of quorum sensing regulatory genes lasR and rhlR. Finally, results obtained from DNA retardation assays provide evidence that AlgR2 can bind specifically to the lasR and rhlR promoters. Altogether, these data provide strong support for the hypothesis that AlgR2 is a global transcriptional regulator in P. aeruginosa.