Glycosylation-associated dysregulation of pyocyanin production in Pseudomonas aeruginosa: Implications for quorum sensing regulation

Abstract

Pseudomonas aeruginosa (P. aeruginosa) is an important opportunistic pathogen associated with high mortality in pneumonia, sepsis, and cystic fibrosis. Lending to its ability to cause severe disease and death is its arsenal of virulence factors and host evasion tactics. In addition to various other regulatory systems, many of P. aeruginosas virulence factors are regulated by a population density dependent regulatory network known as quorum sensing (QS). Many regulatory systems are impacted by post-translational modifications of proteins. An underexplored physiological aspect of P. aeruginosa is its ability to glycosylate proteins and the subsequent impact of glycosylation on P. aeruginosa physiology and behavior. The goal of this study was to determine whether P. aeruginosa QS is regulated by glycosylation. Here we demonstrate that disruption of glycosylation dysregulates QS phenotypes, notably pyocyanin production, in P. aeruginosa PAO1. In this study, it was initially observed that deletion of the P. aeruginosa neuraminidase, PaNA, caused an increased production of pyocyanin in LB-Lennox broth compared to wildtype bacteria at identical population densities. To confirm that the increased pyocyanin production was due to QS, we performed induction experiments using 10% cell-free media harvested from overnight cultures. To determine whether the QS phenotype observed is specific to pseudaminic acid, the target of PaNA, or if it is a reflection of global changes in glycosylation, we measured QS in a library of mutant bacteria generated in an MPAO1 background containing transposon insertions in various glycosyl-associated enzymes. The pattern of dysregulated QS held true in these mutant strains as well. Overall these data indicate that in P. aeruginosa, glycosylation is an important determinant of QS.