Electricity Generation using Iron-Reducing, Haloalkaliphilic Bacteria

Anaerobic, metal-reducing bacteria have been shown to transfer electrons obtained from organic compound oxidation to the surface of electrodes in a microbial fuel cell (MFC), thereby producing current. Such electron shunting ability has been identified in several species of bacteria. The present study used bacteria isolated from a saline, alkaline environment, Soap Lake, Washington, in an MFC. These samples were initially enriched for iron (III) reduction in batch cultures and the enrichments were used to inoculate the anode chamber of the MFC. Scanning electron microscopy showed the bacteria attached to a carbon cloth electrode. Current densities up to 12.5 mA/m 2 were shown to be produced. The open circuit voltage was constant over several days, reaching up to ∼1V. The MFC that was run with uninoculated media showed very little current which dropped within one day. Cyclic voltammetry experiments demonstrated that the bacteria made use of an electron mediator, methylene blue to enhance the transfer of electrons to the anode. Molecular characterization of the partial 16S rRNA gene and RFLP analysis showed that the bacterium responsible was a single species with a 97% similarity to the 16S rRNA gene of Halanaerobium sp