Investigating the mechanisms of surface-induced virulence in Pseudomonas aeruginosa

Abstract

The opportunistic pathogen Pseudomonas aeruginosa increases its virulence in response to surface attachment. This surface-induced virulence is mediated by the cytotoxic alkyl-quinolone (AQ) secondary metabolites, HHQ and PQS. However, the mechanisms in which surface attachment upregulates AQ production remains unknown. In this research, we investigate the possibility that surface attachment increases the translation of the biosynthetic PqsABCDE enzymes which leads to elevated AQ production and virulence. To test this hypothesis, the protein expression of PqsA, the enzyme that catalyzes the first step in AQ production, was visualized by Western blot. Additionally, mass spectrometry was performed to assess global changes in protein levels. Although both Western blot and MS analysis did not demonstrate changes in the PqsABCDE enzymes, the global proteomic analysis did identify a set of regulatory genes that are increased in surface-attached cells. To gain further insight into the signaling pathways responsible for surface-induced virulence, we performed a screen to identify the proteins that mediate surface attachment itself. Of the candidates observed, the pilY1 and phoQ mutants showed reduced surface association in P. aeruginosa. Future investigations of these mechanisms involved in initial attachment and increased AQ secretion may advance the development of anti-infectives.