HR: 1340h
AN: B33A-0844    [Abstracts]
TI: Iron oxidation and biomineralization by Mariprofundus ferrooxydans, a deep-sea microaerophilic lithoautotroph
AU: * Chan, C S
EM: cchan@whoi.edu
AF: Woods Hole Oceanographic Institution, MS 52, Woods Hole, MA 02540, United States
AU: * Chan, C S
EM: cchan@whoi.edu
AF: Bowdoin College, 6800 College Stn, Brunswick, ME 04011, United States
AU: Emerson, D
EM: demerson@bigelow.org
AF: Bigelow Laboratory, PO Box 475, West Boothbay Harbor, ME 04575, United States
AU: Fakra, S
EM: sfakra@lbl.gov
AF: Advanced Light Source, LBNL, Berkeley, CA 94720, United States
AU: Edwards, K J
AF: University of Southern California, 3616 Trousdale Pkwy, Los Angeles, CA 90089, United States
AB: The ocean crust contains a large reservoir of reduced iron, available for microbial energy generation. Some of this ferrous iron is mobilized by fluids in hydrothermal fields at seamounts and mid-ocean ridges. A microaerophilic iron oxidizer, Mariprofundus ferrooxydans has been identified (by molecular methods and microscopy) at various sites, and appears to be a key iron-oxidizing bacterium (FeOB) in the deep sea. Originally isolated from microbial mats near vents at the Loihi Seamount in Hawaii, Mariprofundus is distinctive because it forms an extracellular iron-mineralized stalk-like structure. We aim to understand its metabolism and mineral formation using a multidisciplinary approach, including electron microscopy, x-ray spectroscopy, time-lapse light microscopic imaging of live cells, and genomic and biochemical analyses. Microscopy and spectroscopy work shows that as the cells grow, they excretes iron and organic-rich fibrils that make up the stalk, at a rate of ~2 microns/hr. Stalk growth appears to be parallel to the direction of Fe and oxygen gradients. The Mariprofundus genome contains several terminal oxidases/peroxidases, including two cbb3-type cytochrome oxidases with a high affinity for oxygen, consistent with the microaerophilic lifestyle of these organisms. However, we have not identified genes for metabolisms other than aerobic iron oxidation, nor have we found any genes similar to known or suspected iron oxidases, though the genome (2.87 Mb) is rich in cytochromes (32 of 2922 genes). Thus, we are performing experiments to extract and analyze proteins from both cultured and environmental samples in order to find ones that will oxidize iron. UV-Vis spectra of extracts suggest that c-type cytochromes are particularly abundant, so these are candidates for further investigation. In combination with the microscopy and spectroscopy studies, these are the first steps towards understanding the complete pathway of iron from uptake through mineral formation and growth.
DE: 0419 Biomineralization
DE: 0448 Geomicrobiology
DE: 0460 Marine systems (4800)
DE: 0463 Microbe/mineral interactions
DE: 0465 Microbiology: ecology, physiology and genomics (4840)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting