Sludge oomph: harnessing the power of sediment microbiota

In recent years, new methods of clean and environmentally friendly energy production have been the focus of intense research efforts. Microbial fuel cells are devices that utilize naturally occurring microorganisms that feed on organic matter while producing electrical energy. The natural habitats of bacteria thriving in microbial fuel cells are usually marine and freshwater sediments. In order to develop and improve applications of the vast metabolic repertoire of these microorganisms it is important to identify the relevant proteins and their functional mechanisms. Several sediment bacteria have been the focus of research efforts such as members of the genera Desulfuromonas, Geobacter, and Shewanella. The genomes of these organisms have the common characteristic of containing numerous genes for multiheme cytochromes. For Geobacter and Shewanella many of these are known to be essential for the extracellular respiration that is at the core of electricity production in microbial fuel cells. In this review, the current knowledge on these unusual redox chains and future perspectives on their understanding towards improved extracellular electrical contact are presented