Award: OCE-1635070

Every drop of seawater contains around one million microorganisms (bacteria, small algae and other organisms such as ciliates and diatoms). These marine microbes feed the entire marine ecosystem, modulate global cycles of carbon and other elements, and impact climate. With the advances in genome-sequencing technology, we can now identify the microbes and assess their genetic and metabolic capacities, yet we still cannot deduce from the genomes of these organisms how they will grow - and interact - in nature. We have contributed towards addressing this challenge through a tightly integrated combination of genome scale mathematical modeling, laboratory experiments and field work in the Eastern Mediterranean, which identified genes and pathways dictating how environmentally-relevant microbes grow and interact in the sea. We developed new approaches to model the production and release of metabolites from Prochlorococus, the numerically-dominant photosynthetic bacteria in large swaths of the ocean, and calibrated these models using detailed measurements of key processes in laboratory cultures. We also developed a number of approaches for dealing with missing or imperfect gene annotation in metabolic network models. Long-term co-cultures across the diversity of cultured Alteromonas and Prochlorococcus, analyzed using advanced machine learning techniques, identified differences in the features of the growth curves differentiating between Prochlorococcus strains, with the most important features occurring during culture decline and survival under long-term starvation. Finally, we have studied the changes in microbial populations in the Eastern Mediterranean Sea across seasons, depths and life-styles. Our results suggest that, in the nutrient-poor oceans, in addition to "a-biotic" factors, trophic and organismal interactions, as well as the presence of anthropogenic pollution, may have strong impacts on heterotrophic microbial communities Our results shed light on the dynamics of some of the most common organisms in the world, responsible for the production of up to 20% of the oxygen we breathe. Our collaborative study has fostered the development and training of the next generation of marine scientists, including jointly advised PhD students and postdocs, and the development of a new educational module that shares with high-school students and the general public the excitement of marine research and the need to responsibly utilize and sustain the oceans for the sake of future generations. Last Modified: 02/05/2020 Submitted by: Daniel Segre