HR: 0800h
AN: NS51A-06    [Abstracts]
TI: The role of bacterial nanowires on naturally-occurring electrical fields
AU: Hill, E A
EM: Eric.Hill@pnl.gov
AF: Pacific Northwest National Laboratory, Biological Sciences Division - Microbiology Group, 902 Battelle Blvd., Richland, WA 99352, United States
AU: * Ntarlagiannis, D
EM: dimntar@pegasus.rutgers.edu
AF: Rutgers University, Department of Earth and Environmental Sciences, 101 Warren Street, Newark, NJ 07102, United States
AU: Atekwana, E A
EM: estella.atekwana@okstate.edu
AF: Oklahoma State University, Boone Pickens School of Geology, 105 Noble Research Center, Stillwater, OK 74078, 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
AB: Microbial activity is shown to significantly contribute to the naturally occurring electrical fields observed in geologic media. To investigate the source mechanism of this phenomenon we constructed models of the subsurface by inoculating saturated sand columns with the bacterium Shewanella oneidensis MR-1 and a mutant strain as control. S. oneidensis (and other microoragnisms) are known to develop a structured network of electron- conductive bacterial nanowires as a response to electron acceptor limitation conditions. We show that strong voltage gradients (SP) were concomitant with redox potential gradients in the MR-1 column but absent in the mutant columns. We hypothesize that deeply submerged (suffocating) cells gain access to oxygen through the nanowire network which extends to the groundwater - atmospheric air interface. The nanowires serve as conduits for transfer electrons from bacteria in the anaerobic part of the column to bacteria at the surface that have access to oxygen. We suggest that this process is directly linked with SP and redox gradients that develop across the column. We also observed that in the absence of conductive nanowires (or other conductors) redox potential gradients do not necessarily promote SP gradients as documented in our control columns. Our results suggest that microbial activity and nanowires greatly impact the electrical properties of porous materials and contribute to our understanding of the mechanisms that underlie geophysical methods for mapping microbial activity in near subsurface environments.
DE: 0400 BIOGEOSCIENCES
DE: 0416 Biogeophysics
DE: 5109 Magnetic and electrical properties (0925)
SC: Near-Surface Geophysics [NS]
MN: 2007 Joint Assembly