Award: OCE-1356460

This project explored a recently discovered feature of ocean ecosystems, namely small (~100 nm diameter) membrane vesicles released by microbes living in seawater. Our work has revealed that these discrete, organized structures are released by essentially all marine microbes, and we found that vesicles are abundant in seawater from both coastal and open-ocean environments. Through a series of experiments, we showed that different groups of microbes produce vesicles at different rates, and that environmental conditions can further influence the production of these structures. We conducted detailed examinations of vesicle contents from both natural ocean samples and cultures of the numerically dominant marine cyanobacterium Prochlorococcus, which demonstrated that vesicles can contain a wide range of small molecules, proteins, lipids, and nucleic acids. These inventories suggest a number of potential ecological roles for vesicles in marine systems, including moving genes from one organism to another, facilitating chemical reactions outside the cells, transporting nutrients and biomolecules among cells, and perhaps reducing cell mortality by interfering with viral attacks. The fact that the content of vesicles produced by different microbes is variable suggests that these structures play diverse roles in the ecosystem. Indeed, our data indicate that vesicles are not able to interact equally with all marine microbes, adding a further degree of complexity to the network of vesicle-mediated export, transport and exchange. This work has contributed a new area of study within marine microbial ecology, establishing new paradigms surrounding the mechanisms through which microbes interact with each other and their local extracellular environment. This project has also produced multiple publicly-available datasets on vesicle contents. Broader impacts of this work have included the training of a number of young people, and communicating with the public about the oceans and phytoplankton, through both public lectures, a TED talk, publication of a children's book, and contributions to articles in popular news media outlets. Last Modified: 04/22/2019 Submitted by: Sallie W Chisholm