Approximately one-half of the photosynthesis on Earth occurs in the oceans. Cyanobacteria of the genus Prochlorococcus are among the most abundant marine photosynthetic prokaryotes, contributing a significant fraction of the primary production in open ocean waters and playing a key role in global carbon and energy cycles. Recent sequencing of the complete genomes of several Prochlorococcus and closely related marine Synechococcus strains has revealed that striking genomic differences have evolved within the Prochlorococcus lineage in response to selection pressures present in the ocean environment. Notably, the more recently evolved Prochlorococcus MED4 strain possesses the smallest genome of any oxygenic phototroph and is missing several genes encoding key photosynthetic apparatus and stress response-related proteins. The overarching goal of this project is to establish how genome level differences between Prochlorococcus belonging to the more recently evolved, high light-adapted clade and Prochlorococcus belonging to the low light-adapted clade translate into selective advantages in photosynthetic capacity under specific environmental conditions. Although light and temperature are two critical factors limiting the global distribution of Prochlorococcus, it is unknown how these factors alter photosynthetic processes in Prochlorococcus. State-of-the-art techniques will be used in characterizing the molecular mechanisms underlying temperature and light stress-induced changes in Prochlorococcus (1) photosynthetic capacity (2) photosynthetic membrane and lipid composition, and (3) key photosynthetic apparatus polypeptides. This project will advance our fundamental understanding of photosynthesis in one of the most abundant and ecologically important primary producers on this planet. As a result, it will contribute to efforts aimed at improving our ability to model accurately primary production in ocean ecosystems. This research will also contribute to our basic understanding of the structure, function, and evolution of the photosynthetic apparatus.
Broader Impacts: Numerous undergraduate students will participate in this research over the course of the investigation and this project will serve as an effective educational tool. Through their involvement, students will be exposed to state-of-the-art technology in an exciting field of study and will have the opportunity to participate in national scientific meetings. The ideas and techniques associated with this project will also directly enrich course offerings, and will thus expose a larger group of undergraduates to the importance of scientific research. Moreover, the project participants will continue to participate in ongoing outreach programs and will engage students from rural public schools in mainstream scientific research. This will contribute to local efforts aimed at encouraging students to pursue postsecondary science careers and raising the community's scientific awareness.
