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By Jacob Shirey, Biological Sciences
Advisor: Annette Rowe
Presentation ID: 110
Abstract: Little is known about the mechanisms or importance of extracellular electron transfer (EET) - a process akin to eating or breathing rocks. In marine sediments, these processes are difficult to measure but are likely prevalent. Due to the ecology of their habitat, some microbes have adapted to utilizing inorganic compounds for energy and/or as a terminal electron acceptor for respiration which can result in these processes playing important roles in the biogeochemical cycling of nutrients. In addition, these metabolisms may have biotechnological applications, especially for microbe-electrode technologies such as microbial fuel cells (green, renewable energy). To better understand the mechanisms of EET, a taxonomic and psychologic characterization was carried out on Halomonas strain FeN2, a bacterium capable of EET. Members of the Halomonas genus are Gram-negative, halotolerant, adapted to alkaline environments, and are metabolically versatile. Phylogenetic analysis of 16S rRNA gene sequences indicates that strain FeN2 is most similar to Halomonas alkaliantarctica at 99%. Physiologic experiments demonstrate growth ranging from 4-50°C, 1-10% NaCl, and pH 3-9. FeN2 is capable of heterotrophic growth using acetate as the carbon and electron donor under aerobic (oxygen) and anaerobic (nitrate) conditions. Under aerobic conditions, FeN2 can utilize maltose, citrate, arabinose, and mannose as carbon and electron donors. Chemolithoautotrophic growth with Fe2+ or thiosulfate as electron donors has also been observed. These findings expand our understanding of the metabolic capacity of FeN2 and help lay the groundwork for continued study into the mechanisms and ecological implications of EET in marine sediment microbial communities.