Bacterial extracellular vesicles in marine bacteria

Bacterial extracellular vesicles (BEVs) are spherical membranous structures released by bacterial cells that act as a transport and delivery mechanism for various biological compounds. Experimental investigation of BEVs in marine bacteria, largely limited to a number of laboratory model systems, have suggested putative roles in their ecophysiology. Yet the functional potential of BEVs in their ecological context has never been explored directly in the marine environment. Here we report the results of the first large-scale oceanographic survey of marine BEVs carried out across surface waters of the South Pacific Ocean. The presence of marine BEVs was consistently observed across a range of biogeochemical conditions, with an overall abundance comparable to that of bacterial communities (ca. 108 BEVs L-1). The protein cargoes of marine BEVs differed significantly between environmental conditions, being enriched in carbohydrate transporters and hydrolytic enzymes under phytoplankton bloom conditions, and enriched in different iron uptake proteins in nutrient-limited waters, indicating key extracellular functions they perform in marine bacterial communities. Our observations highlight the importance of marine BEVs and their potential functions across oceanic scales, with implications for our general understanding of key processes in marine microbial ecology.