Bacterial biofilms: the powerhouse of a microbial fuel cell

Research in the field of microbial fuel cells has exploded in recent years and is providing insights into the specialized biological processes that occur within these systems. Fundamental to the functioning of a microbial fuel cell is the formation of highly specialized bacterial biofilms on the electrode surface. While many different bacterial species have been found to associate with electrodes, to date only a few have been isolated in pure culture with the ability to produce a high current density. One such species, Geobacter sulfurreducens, is speculated to form an electrical conductive biofilm capable of electron transfer across a considerable distance greater than 50 µm. The mechanisms for electron transfer across such distances are only just being understood and may involve a matrix of bacterially produced nanowires and/or c-type cytochromes, but limited due to proton accumulation. Evolutionary and genetic engineering studies are now being employed to increase power output on a per cell basis with differing degrees of success.