Anchors away: Determining the role of outer membrane proteins in Pseudomonas aeruginosa vesicle formation
Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes chronic infections in the lungs of individuals with cystic fibrosis (CF). Like many Gram-negatives, P. aeruginosa produces outer membrane vesicles (MVs), which have been shown to package numerous factors including antimicrobial quinolone molecules, toxins, DNA, antibiotic resistance determinants, and cell-cell signaling molecules. The mechanism for the formation of MVs has not been fully elucidated. The Gram-negative outer membrane (OM) contains associated proteins, which anchor it to the peptidoglycan, and keep the OM stable. We hypothesized that peptidoglycan-associated outer membrane lipoproteins OprF, OprL, and OprI contribute to MV formation in P. aeruginosa. In this study, we quantified MVs harvested from oprF, oprL, and oprI mutants. The MV levels produced by the oprL and oprI mutants were not significantly different from those produced by the wild type; however, the oprF mutant showed a three-fold increase in MV production. These data indicate that OprF plays a significant role in anchoring the outer membrane to the peptidoglycan and that, in its absence, more MVs are formed.