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Applied and Environmental Microbiology, October 2008, p. 5943-5947, Vol. 74, No. 19
0099-2240/08/$08.00+0     doi:10.1128/AEM.00961-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Graphite Electrode as a Sole Electron Donor for Reductive Dechlorination of Tetrachlorethene by Geobacter lovleyi{triangledown}

Sarah M. Strycharz,1* Trevor L. Woodard,1 Jessica P. Johnson,1,{dagger} Kelly P. Nevin,1 Robert A. Sanford,3 Frank E. Löffler,2 and Derek R. Lovley1

Department of Microbiology, University of Massachusetts, Amherst, Massachusetts,1 School of Civil and Environmental Engineering and School of Biology, Georgia Institute of Technology, Atlanta, Georgia,2 Department of Geology, University of Illinois at Urbana-Champaign, Urbana, Illinois3

Received 28 April 2008/ Accepted 17 July 2008

The possibility that graphite electrodes can serve as the direct electron donor for microbially catalyzed reductive dechlorination was investigated with Geobacter lovleyi. In an initial evaluation of whether G. lovleyi could interact electronically with graphite electrodes, cells were provided with acetate as the electron donor and an electrode as the sole electron acceptor. Current was produced at levels that were ca. 10-fold lower than those previously reported for Geobacter sulfurreducens under similar conditions, and G. lovleyi anode biofilms were correspondingly thinner. When an electrode poised at –300 mV (versus a standard hydrogen electrode) was provided as the electron donor, G. lovleyi effectively reduced fumarate to succinate. The stoichiometry of electrons consumed to succinate produced was 2:1, the ratio expected if the electrode served as the sole electron donor for fumarate reduction. G. lovleyi effectively reduced tetrachloroethene (PCE) to cis-dichloroethene with a poised electrode as the sole electron donor at rates comparable to those obtained when acetate serves as the electron donor. Cells were less abundant on the electrodes when the electrodes served as an electron donor than when they served as an electron acceptor. PCE was not reduced in controls without cells or when the current supply to cells was interrupted. These results demonstrate that G. lovleyi can use a poised electrode as a direct electron donor for reductive dechlorination of PCE. The ability to colocalize dechlorinating microorganisms with electrodes has several potential advantages for bioremediation of subsurface chlorinated contaminants, especially in source zones where electron donor delivery is challenging and often limits dechlorination.

* Corresponding author. Mailing address: 422D Morrill 4 North, 639 N. Pleasant St., Amherst, MA 01003. Phone: (413) 577-2440. Fax: (413) 577-4660. E-mail: strychar{at}microbio.umass.edu

{triangledown} Published ahead of print on 25 July 2008.

{dagger} Present address: Mascoma Corporation, Lebanon, NH.

Applied and Environmental Microbiology, October 2008, p. 5943-5947, Vol. 74, No. 19
0099-2240/08/$08.00+0     doi:10.1128/AEM.00961-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.





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