Electrically conductive bacterial nanowires produced by Shewanella oneidensis strain MR-1 and other microorganisms

*Pacific Northwest National Laboratory, Richland, WA 99352;
^‡Department of Molecular and Cellular Biology, University of Guelph, Guelph, ON, Canada N1G 2W1;
^¶Water Environment and Remediation Research Center, Korea Institute of Science and Technology, Seoul 136-791, Korea;
^§Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea;
^‖Department of Biological Sciences, University of Wisconsin, Milwaukee, WI 53211;
**Department of Agriculture Biochemistry, University of Missouri, Columbia, MO 65211;
^††Marine Biotechnology Institute, Heita, Kamaishi, Iwate 026-0001, Japan;
^‡‡Department of Environmental Engineering, Pennsylvania State University, University Park, PA 16802; and
^§§Department of Earth Sciences, University of Southern California, Los Angeles, CA 90089

Communicated by J. Woodland Hastings, Harvard University, Cambridge, MA, June 6, 2006 (received for review September 20, 2005)

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Fig. 1.
Wild-type strain MR-1 taken from an electron-acceptor-limited chemostat operating at low agitation (50 rpm). (A) SEM image of MRI. (B) Epifluorescence micrograph of MR-1 stained with the fluorescent nonspecific protein-binding stain NanoOrange in liquid medium.
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Fig. 2.
STM images of isolated nanowires from wild-type MR-1, with lateral diameter of 100 nm and a topographic height of between 5 and 10 nm. (A) Arrows indicate the location of a nanowire and a step on the graphite substrate. (B) Higher magnification showing ridges and troughs running along the long axis of the structures.
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Fig. 3.
Transmission EM images of whole mounts of MR-1 cells incubated in an aqueous suspension of Si-HFO. The Si-HFO was transformed to nanocrystalline magnetite along extracellular features consistent with the dimensions of nanowires.
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Fig. 4.
SEM and STM images of nanowires produced by cyanobacteria and methanogenic cocultures. (A) SEM image of Synechocystis sp. PCC 6803 cultivated with CO₂ limitation and excess light. (B) STM imagery confirms that the extracellular appendages produced under these conditions are highly electrically conductive, with morphological similarities to nanowires produced by S. oneidensis MR-1. (C) SEM image of P. thermopropionicum and M. thermoautotrophicus (arrow) in methanogenic cocultures showing nanowires connecting the two genera, as reported by Ishii et al. (12). (D) STM images confirm that these nanowires are highly conductive and composed of bundles of individual filaments.

Footnotes

^†To whom correspondence should be addressed at:
Biological Sciences Division, Pacific Northwest National Laboratory, P.O. Box 999, MS: P7-50, Richland, WA 99352.
E-mail: yuri.gorby{at}pnl.gov