Electrochemically Active Soluble Mediators from Shewanella oneidensis: Relevance to Microbial Fuel Cells and Extracellular Electron Transfer

: Chemotrophic microorganisms harvest energy from their growth substrates through coupled redox reactions that shuttle electrons to terminal electron acceptors. Classic aerobic and anaerobic respiratory chains are well studied and understood. Select bacteria are able to use insoluble metal ions as terminal electron acceptors. The respiration style requires a mechanism that effectively promotes extra-cellular electron transfer to support cell function and growth. One mechanism microbes utilize resembles physical wiring where the microbe grows fine conductive appendages that appear able to allow electron transfer from the cell to the metal ion acceptor1. A second approach is the use of soluble mediators such as, quinones, phenazines, and riboflavin, which are able to shuttle electrons from the cell to the terminal acceptor 2. Understanding electrochemistry of extra-cellular electron transfer is relevant to predicting environmental biogeochemical cycles, as well as in engineering issues for biologically initiated corrosion and the development of microbial fuel cells.