Shewanella oneidensis MR-1 Msh pilin proteins are involved in extracellular electron transfer in microbial fuel cells

Shewanella is a microbial genus that can oxidize lactate for the reduction of insoluble electron acceptors. This reduction is possible by either direct (cell-surface interaction, nanowires) or indirect (soluble redox mediators) mechanisms. However, the actual molecular identification of a nanowire has not been determined. Through mutational studies, Shewanella oneidensis MR-1 was analyzed for its ability to transfer electrons to an electrode after deletion of the structural pilin genes (Delta mshA-Delta) or the entire biosynthetic expression system (Delta mshH-Q) of one of its pilin complexes (Msh type IV pilus gene locus). The complete removal of the Msh complex (Delta mshH-Q) significantly decreased the current generated from a fuel cell compared to MR-1. However, the mutant with only extracellular Msh structural proteins removed (Delta mshA-D) was able to generate 80% of the current compared to MR-1. Thus, the intracellular and membrane bound Msh biogenesis complex is a pathway for extracellular electron transfer in S. oneidensis MR-1. Published by Elsevier Ltd.