HR: 0800h
AN: NS51A-05    [Abstracts]
TI: Are Microbial Nanowires Responsible for Geoelectrical Changes at Hydrocarbon Contaminated Sites?
AU: * Hager, C
EM: christine.hager@okstate.edu
AF: Boone Pickens School of Geology, 105 Noble Research Center Oklahoma State University, Stillwater, OK 74078-3031, United States
AU: Atekwana, E A
EM: estella.atekwana@okstate.edu
AF: Boone Pickens School of Geology, 105 Noble Research Center Oklahoma State University, Stillwater, OK 74078-3031, United States
AU: Gorby, Y A
EM: ygorby@venterinstitute.org
AF: J. Craig Venter Institute, 11149 North Torrey Pines Road, La Jolla, CA 92037, United States
AU: Duris, J W
EM: jwduris@usgs.gov
AF: U.S. Geological Survey, 6520 Mercantile Way, Suite 5, Lansing, MI 48911-5991, United States
AU: Allen, J P
AF: Department of Biological Sciences, Western Michigan University, Kalamazoo, MI 49008- 5410, United States
AU: Atekwana, E A
EM: eliot.atekwana@okstate.edu
AF: Boone Pickens School of Geology, 105 Noble Research Center Oklahoma State University, Stillwater, OK 74078-3031, United States
AU: Ownby, C
EM: charlotte.ownby@okstate.edu
AF: Boone Pickens School of Geology, 105 Noble Research Center Oklahoma State University, Stillwater, OK 74078-3031, United States
AU: Rossbach, S
EM: silvia.rossbach@wmich.edu
AF: Department of Biological Sciences, Western Michigan University, Kalamazoo, MI 49008- 5410, United States
AB: Significant advances in near-surface geophysics and biogeophysics in particular, have clearly established a link between geoelectrical response and the growth and enzymatic activities of microbes in geologic media. Recent studies from hydrocarbon contaminated sites suggest that the activities of distinct microbial populations, specifically syntrophic, sulfate reducing, and dissimilatory iron reducing microbial populations are a contributing factor to elevated sediment conductivity. However, a fundamental mechanistic understanding of the processes and sources resulting in the measured electrical response remains uncertain. The recent discovery of bacterial nanowires and their electron transport capabilities suggest that if bacterial nanowires permeate the subsurface, they may in part be responsible for the anomalous conductivity response. In this study we investigated the microbial population structure, the presence of nanowires, and microbial-induced alterations of a hydrocarbon contaminated environment and relate them to the sediments' geoelectrical response. Our results show that microbial communities varied substantially along the vertical gradient and at depths where hydrocarbons saturated the sediments, ribosomal intergenic spacer analysis (RISA) revealed signatures of microbial communities adapted to hydrocarbon impact. In contrast, RISA profiles from a background location showed little community variations with depth. While all sites showed evidence of microbial activity, a scanning electron microscope (SEM) study of sediment from the contaminated location showed pervasive development of "nanowire-like structures" with morphologies consistent with nanowires from laboratory experiments. SEM analysis suggests extensive alteration of the sediments by microbial Activity. We conclude that, excess organic carbon (electron donor) but limited electron acceptors in these environments cause microorganisms to produce nanowires to shuttle the electrons as they seek for distant electron acceptors. Hence, electron flow via bacterial nanowires may contribute to the geoelectrical response.
DE: 0400 BIOGEOSCIENCES
DE: 0416 Biogeophysics
DE: 0418 Bioremediation
DE: 0432 Contaminant and organic biogeochemistry (0792)
DE: 0448 Geomicrobiology
SC: Near-Surface Geophysics [NS]
MN: 2007 Joint Assembly