Heme uptake by marine bacteria: A molecular-level study of an oceanic iron recycling pathway

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Understanding the mechanisms of assimilation of nutrients by marine microorganisms is important to marine science, especially for the micronutrient iron (Fe), which is often present in limiting concentrations in marine surface waters. Much of the Fe is ocean water is complexed to organic ligands and recent studies have examined the capabilities of marine bacteria to assimilate these different forms of Fe. One potential source of Fe is through the assimilation of heme, a Fe-containing biochemical, and it has been recently shown that marine bacteria have transport systems for heme uptake. This project is therefore aimed at examining if Fe is assimilated as heme and whether this is an important pathway for iron accumulation by marine microorganisms. The potential for heme uptake will be examined in laboratory culture studies. Genetic tools and manipulations will be used to identify the uptake mechanisms, demonstrate their activity and show whether this is an important assimilation pathway. These approaches will also be used to examine the extent of this pathway in natural marine microbial communities.This proposal will integrate its activities with the NSF-funded Center for Ocean Science Education Excellence - California (COSEE CA) and with Scripps Educational Alliances to extend the research impact to K-12 public education. A Research Experiences for Teachers relationship has already been established through these interactions with teachers at University City High School in San Diego. This research will also support for a graduate student whose PhD thesis will focus on this research. The scientific broader impacts of this research relate to understanding the ocean biogeochemistry of Fe and the chemical-biological linkages, and the role of limiting nutrients on the global biogeochemistry of the ocean.