Award: OCE-1538628

Intellectual Merit Bacteria free living in seawater are some of the most abundant organisms on our planet, at times making up communities of over a million cells per milliliter of seawater. These microorganisms form the base of the food web in many marine environments, and are vital components for healthy ecosystem functioning. Rather than forming infinitely diverse assemblages, research over the past three decades has shown that a relatively small number of groups of microorganisms dominate seawater microbial communities from the poles to the tropics. Thus, understanding the characteristics of this limited number of groups is an integral aspect of understanding marine ecosystems across the globe. One of these, a group of marine bacteria known as SAR11, is one of the most abundant organisms on Earth, were at times it makes up over 50% of the microbial cells inhabiting surface seawater environments. While originally known by only DNA sequences, nearly two decades ago strains of the SAR11 clade were brought in to laboratory culture for the first time using a novel culturing approach which allowed for their detailed investigation in a controlled laboratory setting. Unfortunately, to date studies reporting the isolation of SAR11 strains remain few. Within each major group of marine bacteria, different "types" have been found to occur at different times, geographic locations, or depths in the water column. Some of these differences in ecology appear to coincide with differences in genetic makeup. However, an outstanding question in marine ecology is how genetic diversity within bacterial groups such as SAR11 is generated, propagated, retained, or lost. In this study we combined new DNA sequencing technologies with new microbial cultivation techniques to investigate the eco-evolutionary characteristics of one of our planet’s most abundant organisms. Through this work, we have created an unprecedented dataset that should provide additional insights for years to come. Our cultivation experiments also provided the additional benefit of generating isolated strains from several other important groups of marine bacteria, including the first isolates of the SAR86 clade, that are now available to the broader scientific community. Broader Impacts This project directly supported the training and professional development of two postdoctoral scholars, three graduate students, numerous undergraduates, and one junior faculty member. It has provided, or will continue to provide, organized opportunities for interdisciplinary training, participation in scientific meetings, and scientific publications. This project also formed the basis for formal classroom activities at the University of Hawaii, as well as outreach endeavors to the public. The culture collection and associated genomic resources will serve as a resource for the broader scientific community for years to come. Last Modified: 02/27/2020 Submitted by: Michael S Rappe