Proteomic and Functional Analyses of Outer Membrane Vesicles Secreted by Vibrio splendidus

Vibrio splendidus is an important opportunistic pathogen ubiquitously present in the marine environment, exhibiting virulence to a variety of cultured animals. The extracellular products secreted by V. splendidus are crucial to bacterial survival and virulence. In this study, the secretion of outer membrane vesicles (OMVs) by V. splendidus was determined, purified, and morphologically characterized. The protein composition of OMVs was analyzed by proteomic analysis. The results showed that approximately 120 proteins were contained in these OMVs, including outer membrane proteins, flagellins, ABC transporters, protease, and iron regulation proteins, etc., which were involved in bacterial motility, formation of biofilms and the cell membrane components, and cellular localization based on their structural molecule activity, passive transmembrane transporter activity, channel activity, neurotrans- mitter receptor activity, extracellular ligand-gated ion channel activity, glutamate receptor activity, ligand-gated ion channel activity, and transmembrane signaling receptor activity. To explore the biological functions of OMVs in V. splendidus, the effects of OMVs on the bacterial adaption to iron limitation, antibiotic, and the coelomic fluid of the Apostichopus japonicus were confirmed. This study is the first time to show that V. splendidus secretes OMVs, and OMVs carry functional proteins that enhance bacterial survival under various stresses.