Electrodes as electron donors for respiration and bioremediation

Under the appropriate reducing conditions on an electrode, Geobacter sp. may use electrodes as electron donors. This metabolism may also serve as a strategy for bioremediation of heavy metals under electron-donor limited conditions. Electrodes as electron donors for respiration and bioremediation were studied. The live sediment inoculation from the Connecticut River resulted in consumption of electrical current from the poised electrode and depletion of nitrate. When the medium was replaced, current and nitrate consumption resumed without lag. The reduction of nitrate resulted in the production of nitrate and a stoichiometric consumption of electrons from the electrode. 16S rDNA sequences, most closely related to known members of the family Geobacteraceae, predominated on electrodes to which current was supplied. When a pure culture of G. metallireducens was provided a poised electrode as the electron donor for nitrate reduction, current consumption was concomitant with nitrate reduction. The stoichiometry of electron consumption was consistent with the production of nitrite. Under electron donor-limited conditions, the addition of acetate has been shown to stimulate the reduction and immobilization of uranium in situ. The presence of G. sulfurreducens on the working electrode prevented the rapid remobilization of uranium from the electrodes when the cathode was depolarized. Electrodes might support the in situ immobilization of uranium as a novel bioremediation strategy. This is an abstract of a paper presented at the 228th ACS National Meeting (Philadelphia, PA 8/22-26/2004).