Project: Collaborative Research: Microdiversity drives ecosystem function: SAR11 bacteria as models for oceanic nitrogen loss

NSF Award Abstract:
This project studies how low oxygen availability influences the biodiversity and ecological role of SAR11 bacteria, one of the most abundant microbial groups in the ocean. The work involves oceanographic sampling across a range of oxygen and nutrient levels in the Eastern Tropical North Pacific Ocean. Using a combination of genomic, microbiological, and biogeochemical methods, the study identifies the mechanisms by which SAR11 strains diversify into separate niches and species and contribute biochemically to the ecosystem, likely through removing nitrogen from seawater. The project equips the next generation of researchers and educators, notably those from underrepresented minority groups, to use oceanographic, genomic, and microbiological concepts to meet contemporary scientific challenges. This goal is met through a combination of bioinformatic workshops that target undergraduate students from the University System of Puerto Rico, middle school teacher-training workshops, and middle or high school teacher internships in the investigator’s labs. This multifaceted research and educational agenda fills a gap in our understanding of marine biological diversity, identifies the contribution of SAR11 bacteria to nutrient and carbon cycles in low oxygen oceans, and provides lessons and analytical tools to study microbial processes in other ecosystems.

This project has two aims. Aim 1 employs comparative metagenomic and single-cell genomic analyses to identify metabolic properties that distinguish SAR11 clades from low oxygen regions and processes of selection or gene flow operating across the clades. Aim 2 combines microbial transcriptomics, incubation experiments with isotope tracers, and culturing to delimit the oxygen and nutrient conditions that define the niche space of each SAR11 clade and to correlate SAR11 gene transcription with community biochemical outcomes, including nitrogen loss through denitrification. The results of these aims and the informatic methods used to probe microbial microdiversity are disseminated through genomics-focused undergraduate workshops, and new teacher-training educational modules, including lab-based modules focused on the importance of microorganisms under environmental change in the oceans. Data, manuscripts, and informatics workflows from this project are made publicly available. The results are critical for resolving the processes that create and sustain microbial diversity in the oceans and informing biogeochemical models that predict how diversity influences ecosystem processes.

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.