Project: Illuminating the physiology, cellular characteristics, and ecogenomics of the first cultivated strain of the SAR86 lineage

NSF Award Abstract:
Since their initial discovery nearly 30 years ago, a group of marine bacteria known as SAR86 has come to be recognized as one of the main groups of microorganisms inhabiting the global surface ocean, where they can make up 20% or more of the planktonic cells that live in seawater. SAR86 cells appear to employ a heterotrophic lifestyle wherein the energy for cellular growth and metabolism is derived from organic compounds, and oxygen is converted to carbon dioxide via aerobic respiration. This basal metabolism appears to be supplemented by harvesting energy from sunlight using a unique light-harvesting system based on a protein known as proteorhodopsin. Despite its global prevalence and thus importance to understanding Earth’s major elemental cycles, a major factor that limits understanding of SAR86 marine bacteria is the lack of cultured isolates, such that even the most basic cellular features and metabolic traits are unknown. This study leverages the first isolated strain from the SAR86 lineage in a set of experiments designed to characterize basic aspects of SAR86 cells and to link metabolic traits with specific genetic features of SAR86. Collectively, these experiments are increasing understanding of one of the global-ocean’s most abundant microbial inhabitants. This project also supports the maintenance and public dissemination of a culture collection of marine microorganisms at the University of Hawaiʻi, the development of an educational module that focuses on the ecology of marine microbes inhabiting coastal Hawaiʻi, and the collaboration of the research team with community education partners on a new 3-D virtual reality rendering of the research laboratory and institute. One postdoctoral researcher, one graduate student, and multiple undergraduates are being trained in engaging, cutting-edge research, including the exposure of undergraduate students of native Hawaiian and Pacific Island ancestry to hands-on research and training.

The project uses living cultures and the closed, annotated genome of the first isolated strain of the enigmatic SAR86 clade, HIMB1674, in a set of experiments to provide fundamental information on the cellular and physiological characteristics of SAR86 cells and connect specific metabolic features to genes and pathways encoded by the genome. The project links the genome of HIMB1674 to publicly available genomes and metagenomes from around the globe and integrates SAR86 eco-genomics into a time-series study that spans a steep coastal to open-ocean environmental gradient in the tropical Pacific Ocean. The experiments offer a combination of dry-lab informatic analyses, wet-lab experimentation with cultures, and a field program that uniquely illuminates the systems biology of SAR86 marine bacteria. The three main goals of this project are to 1) use SAR86 strain HIMB1674 to quantify basic cellular characteristics and investigate specific metabolic features predicted from its genome, 3) use the complete genome sequence of strain HIMB1674 as an anchor to investigate the eco-evolutionary characteristics of the SAR86 lineage, and 3) perform experiments designed to isolate additional SAR86 strains.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.