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.

Microbial Fuel Cells, A Current Review

“…G. lovleyi and Anaeromyxobacter dehalogenans have been shown to reduce chlorinated compounds with as electrode as the sole source of electrons [142,143]. Field trials have also shown that electrons provide by an electrode can improve uranium removal in contaminated sites [127].…”

Bacterial community structure corresponds to performance during cathodic nitrate reduction

“…Consequently, it is likely that bacteria reducing nitrate at cathodes powered by anodic reactions access electrons from the cathode and not through hydrogen. Our current knowledge of bacterial denitrification reactions relevant to BES cathodes is based on pure-culture studies of chemolithotrophic denitrification coupled to inorganic electron donors (Fernández et al, 2008;Weber et al, 2006) and cathodes as electron donors for anaerobic respiration (Gregory et al, 2004;Thrash et al, 2007;Strycharz et al, 2008;Thrash and Coates, 2008;He et al, 2009). Presently, only two studies examined microbial biofilm communities in denitrifying BESs (Gregory et al, 2004;Park et al, 2006).…”

Potentiostatically Poised Electrodes Mimic Iron Oxide and Interact with Soil Microbial Communities to Alter the Biogeochemistry of Arctic Peat Soils

“…These bacteria achieve extracellular electron transfer through a variety of different mechanisms and can be utilized to produce power in microbial fuel cells [17][18][19], produce chemicals in microbial electrolysis cells [20][21][22], and remediate organic contaminants in the subsurface [23][24][25][26]. While humans have successfully exploited the ability of microbes to perform extracellular electron transfer in bioengineered systems, the role that extracellular electron transfer plays in natural environments, such as soils, is less clear [27].…”