title: Graphite electrode as a sole electron donor for reductive dechlorination of tetrachlorethene by Geobacter lovleyi.
abstract: 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.
authors.affiliation: Department of Microbiology, University of Massachusetts, Amherst, Massachusetts, USA. strychar@microbio.umass.edu
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Strycharz
authors.forename: Trevor L
authors.initials: TL
authors.lastname: Woodard
authors.forename: Jessica P
authors.initials: JP
authors.lastname: Johnson
authors.forename: Kelly P
authors.initials: KP
authors.lastname: Nevin
authors.forename: Robert A
authors.initials: RA
authors.lastname: Sanford
authors.forename: Frank E
authors.initials: FE
authors.lastname: Löffler
authors.forename: Derek R
authors.initials: DR
authors.lastname: Lovley
mesh_terms: D019342:Acetic Acid / Q000378:metabolism; D018441:Biofilms / Q000254:growth & development; D018533:Biomass; D004560:Electricity; D004566:Electrodes / Q000382:microbiology*; D004583:Electrons; D005025:Ethylene Dichlorides / Q000378:metabolism; D005650:Fumarates / Q000378:metabolism; D045302:Geobacter / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D006108:Graphite / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D019802:Succinic Acid / Q000378:metabolism; D013750:Tetrachloroethylene / Q000378:metabolism*
chemical_list: D005025:Ethylene Dichlorides; D005650:Fumarates; D006108:Graphite; C032005:fumaric acid; D019802:Succinic Acid; D019342:Acetic Acid; D013750:Tetrachloroethylene