Investigations into the extracellular electron transfer mechanisms of Geobacter and Shewanella species

With the recent discoveries that electrochemically active bacteria may use conducting nanofilaments and/or soluble electron mediators to enhance electron transport to insoluble electron acceptors, the elucidation of the mechanism for extracellular electron transfer (EET) has become complex. We have studied both Shewanella oneidensis MR-1 and Geobacter sulfurreducens DL-1 using nanoscale and macroscopic electrochemical techniques to determine how the EET mechanisms change under different environmental conditions. By performing these analytical experiments while exposing the microorganisms to differing levels of oxygen (MR-1), nutrients (MR-1, DL-1) and electron acceptors (MR-1, DL-1), we have made conclusions about when cell attachment occurs and biofilms are formed, when conducting nanofilaments are present, and when extracellular electron transfer is enhanced or reduced. We also used novel strains and deletion mutants to help understand the role different electron transfer mechanisms play in current generation in MFCs.