Geobacterspecies have a number of important bioenergy applications. Recent studies have demonstrated that they can be abundant components of the microbial aggregates that form in anaerobic digestors converting organic wastes to methane. They can act as syntrophs, degrading organic compounds to acetate that methanogens in the aggregates then consume to produce methane. Electrons derived from Geobacter metabolism may be fed directly to the methanogens through electrically conductive networks that have been detected within the aggregates.
Some Geobacter species are capable of electrosynthesis, using electrons derived from electrodes to reduce carbon dioxide to fuels or other useful organic compounds.
One of the most studied bioenergy applications of Geobacter species is their ability to oxidize organic compounds with electron transfer to electrodes. Geobacter species were the first microorganisms found to derive energy to support growth from organic matter oxidation with an electrode serving as the sole electron acceptor and can produce the highest current densities of any pure culture. Geobacter species are often the microorganisms most highly enriched on electrodes harvesting electricity from a diversity of environments. Geobacter sulfurreducens has become the organism of choice for studying the mechanisms for direct electron transfer from microbial biofilms to electrodes. Recent studies have demonstrated that it produces highly conductive biofilms that promote electron transfer to the electrode and releases the c-type cytochrome, OmcZ, which accumulates at the biofilm-electrode interface to promote electron transfer to the electrode.