Collaborative Research: Loihi Seamount as an Observatory for the Study of Neutrophilic Iron-Oxidizing Bacteria and the Microbial Iron Cycle

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AbstractThe importance of metals to life has long been appreciated. Iron (Fe) is the fourth most abundant element, and the second most abundant redox-active element in Earth's crust, rendering it the most important environmental metal. In recognition of this, a recent surge in research on microbial Fe redox transformations in the environment has resulted in many exciting discoveries and enhanced appreciation for the importance of these processes (Lovley 2000). Most of these studies, however, have focused on the reductive Fe cycle and organisms such as the Geobacteraceae. This is in part because Fe-oxidizing organisms, particularly those who inhabit circumneutral pH habitats, have been notoriously difficult to culture and study in the lab. However, recent successes on this front have resulted in the isolation of a number of novel chemolithoautotrophic Fe-oxidizing bacteria (FeOB). Studies of these bacteria have revealed a remarkable diversity, both physiologically and phylogenetically. This perhaps should not be surprising given that Fe is the most abundant lithoautotrophic energy source in Earth's crust, but is not in keeping with the present attention given to their study. This project is initiating a microbial observatory for the study of iron-oxidizing bacteria (.FeMO.) at the Hawaiian Seamount, Loihi. The major purpose of the project is to elucidate the full physiological, phylogenetic, and biochemical diversity of this group of prokaryotes. Loihi was selected as the study site because: (1) FeOB have been recognized and studied there previously; (2) Loihi displays a wide-range of FeOB habitats: from hydrothermal fluids to rocks, from low-flow, low-T (10C) seeps to high-flow, high-T (60 C) vents; (3) previous studies provided an excellent geochemical framework on which to base these studies; and (4) Loihi is very accessible, located only 25 miles SW of the big island of Hawaii. The research group represents a cross-section of expertise on FeOB. Principal components of the FeMO project include (1) cultural analysis of FeOB, (2) kinetic studies on Fe-oxidation rates, (3) biochemical studies on the Fe oxidase, and (4) biogeochemical studies on colonization and solid rock utilization by FeOB. Microbial Fe redox transformations are well known to impact environmental and human health, for example in organic contaminant degradation and via sorption of toxic radionucleotides, particularly in terrestrial and coastal marine habitats. In the more poorly studied, oligotrophic deep-sea, chemoautotrophic FeOB have recently been recognized for their potentially important role in production of new biomass carbon. This research is leading to significant advances in the study of FeOB and understanding their environmental activities and capabilities, and would enable more accurate predictions about them in many poorly-accessible habitats. The FeMO PIs are involved heavily in middle and high-school teacher education and enhancement efforts at WHOI. These include participation in existing summer workshops, the development of a new school-year weekend mini-workshop, and the direct involvement of a teacher in the FeMO fieldwork. FeMO participants are also strongly involved with higher education on multiple fronts, including the specific recruitment of female and minority undergraduates from a New England women's college (Smith) for summer internships via the Praxis program.