A PQS-Cleaving Quorum Quenching Enzyme Targets Extracellular Membrane Vesicles of Pseudomonas aeruginosa

Abstract

The opportunistic pathogen Pseudomonas aeruginosa uses quorum sensing to control its virulence. One of its major signal molecules, the Pseudomonas quinolone signal PQS, has high affinity to membranes and is known to be trafficked mainly via outer membrane vesicles (OMVs). We previously reported that several 3-hydroxy-4(1H)-quinolone 2,4-dioxygenases (HQDs) catalyze the cleavage of PQS and thus act as quorum quenching enzymes. Further analysis showed that, in contrast to other HQDs, the activity of HQD from Streptomyces bingchenggensis (HQDS.b.) was unexpectedly stabilized by culture supernatants of P. aeruginosa. Interestingly, the stabilizing effect was higher with supernatants from the strain PA14 than with supernatants from the strain PAO1. Heat treatment and lyophilization hardly affected the stabilizing effect; however, fractionation of the supernatant excluded small molecules as stabilizing agents. In a pull-down assay, HQDS.b. appeared to interact with several P. aeruginosa proteins previously found in the OMV proteome. This prompted us to probe the physical interaction of HQDS.b. with prepared extracellular membrane vesicles. Homo-FRET of fluorescently labeled HQDS.b. indeed indicated a spatial clustering of the protein on the vesicles. Binding of a PQS-cleaving enzyme to the OMVs of P. aeruginosa may enhance PQS degradation and is highly reconcilable with its function as a quorum quenching enzyme.

Bacterial extracellular vesicles: A position paper by the microbial vesicles task force of the Chinese society for extracellular vesicles

“…45 Recent studies have shown that Pseudomonas quinolone signal (PQS) is closely related to OMVs. 50 PQS also induced substantial release of MVs in all strains. 51 These OMVs can interact with other cells and release PQS into the surrounding environment.…”

“…Recent studies have shown that Pseudomonas quinolone signal (PQS) is closely related to OMVs 50 . PQS also induced substantial release of MVs in all strains 51 .…”

Evaluation of the production potential of quorum quenchig enzymes of extremophile bacteria from Antarctica

“…When cell density is high, the accumulation of the signal in the extracellular medium allows the activation of a cellular response [1][2]. This system regulates various functions that require the concerted action of numerous cells such as bioluminescence, production of secondary metabolites, sporulation, biofilm formation, antibiotic resistance, and production of multiple virulence factors [3]. QS signal molecules are chemically diverse and characterized by having a low molecular weight [4].…”