Role of PvdQ in Pseudomonas aeruginosa virulence under iron-limiting conditions

Abstract

PvdQ, an acylase fromPseudomonas aeruginosaPAO1, has been shown to have at least two functions. It can act as a quorum quencher due to its ability to degrade long-chainN-acylhomoserine lactones (AHLs), e.g. 3-oxo-C12-HSL, leading to a decrease in virulence factors. In addition, PvdQ is involved in iron homeostasis by playing a role in the biosynthesis of pyoverdine, the major siderophore ofP. aeruginosa. In accordance with earlier studies on RNA level, we could show at the protein level that PvdQ is only expressed when iron is present at very low concentrations. We therefore set out to investigate the two functions of PvdQ under iron-limiting conditions. Gene deletion ofpvdQdoes not affect growth ofP. aeruginosabut abrogates pyoverdine production, and results in an accumulation of 3-oxo-C12-HSL. Phenotypic analyses of our ΔpvdQmutant at low iron concentrations revealed that this mutant is impaired in swarming motility and biofilm formation. Additionally, a plant and aCaenorhabditis elegansinfection model demonstrated that the deletion ofpvdQresulted in reduced virulence. None of the phenotypes in the present study could be linked to the presence or absence of AHLs. These results clearly indicate that under iron-limiting conditions PvdQ plays a major role in swarming motility, in biofilm development and in infection that is more likely to be linked to the pyoverdine pathway rather than the LasI/LasR/3-oxo-C12-HSL quorum-sensing circuit.