OCE-PRF Track 1 (Broadening Participation): Impact of Phytoplankton-Bacteria Interactions on Metal Bioavailability

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In this two year postdoctoral research fellowship, the fellow will analyze how bacteria-picophytoplankton interactions impact the utilization of trace metals from desert dust. Results of these experiments will elucidate biological advantages conferred by the production of metal chelators, as it reveals the role that bacteria play in phytoplankton metal acquisition, and will advance understanding in oceanic primary production and carbon cycling. The fellow will broaden participation of under-represented groups in ocean sciences at local high schools and diversity-serving colleges through teaching modules and research internships focusing on the ocean sciences and marine trace metal nutrition. The fellow is being hosted by sponsoring scientist Dr. Mak Saito at Woods Hole Oceanographic Institution.The research examines how the interactions between bacteria and phytoplankton modulate the bioavailability of metals from desert dust, and thus impact metal uptake and the growth of phytoplankton. The work addresses the following hypothesis: The presence of bacteria in picophytoplankton cultures will (a) enable iron and cobalt solubilization, (b) spur picophytoplankton metal uptake and growth, and (c) lead to expression of iron uptake transporters which more closely resembles their expression in the natural marine environment. Specifically, the picoeukaryote Ostreococcus and the cyanobacterium Crocosphaera will be grown in semi-continuous cultures under axenic conditions (control), with bacterial isolates (laboratory culture experiments) and in the presence of natural bacterial populations (shipboard culture experiments), with and without addition of desert dust, under trace metal clean conditions. Ostreococcus and Crocosphaera are representative model organisms for processes of picoeukaryotic photosynthesis and nitrogen fixation. Treatment effects on growth rate, metal uptake, and ligand conditional stability constants will be measured. Siderophore transporters and other proteins involved in iron uptake will be detected by proteomic methods. Further, a differential and quantitative proteomic approach will allow for the detection of proteins involved in iron uptake in subsurface ocean samples, in order to compare to the transporters and transporter expression levels of experimental cultures.