Membrane Vesicles Produced by Marine Bacteria: Origins, Distributions and Functions

Some bacteria are known to release small amounts of their cell envelope in the form of tiny (< 200 nm diameter) spherical structures known as membrane vesicles. While the functions of these vesicles have been explored in pathogens, nothing is known about their abundance or roles in marine ecosystems. The investigators have recently demonstrated that Prochlorococcus, the numerically dominant photosynthetic cell in the world's oceans releases membrane vesicles continually during growth, and they have shown that these structures are indeed found in abundance in ocean samples. Bacterially produced membrane vesicles represent a major new feature of ocean ecosystems and could provide important clues about the network of interactions among microbes and their environment. Prochlorococcus vesicles contain diverse macromolecules, including lipids, proteins, and nucleic acids, suggesting that these structures could play many varied roles within marine microbial communities. The researchers will use the Prochlorococcus model system and the analysis of natural seawater samples from several field sites to address fundamental questions about the production and function of membrane vesicles in the oceans. The overarching questions motivating this study include:

What environmental factors influence the rate of release of membrane vesicles by Prochlorococcus, and what can this tell us about the regulation of this process?

How does vesicle abundance vary in different regions of the oceans?

What DNA is found in vesicles from natural seawater samples? How does the vesicle "metagenome" compare to the bacterial metagenome, and what can this tell us about the diversity of organisms that release vesicles?

What ecological roles might vesicles play in marine microbial ecosystems? Can they facilitate horizontal gene transfer? Can they act as a "decoy" to reduce phage predation?