An electricity-generating prosthecate bacterium strain Mfc52 isolated from a microbial fuel cell.

Rod-shaped Alphaproteobacteria possessing long prosthecae-like appendages have been detected abundantly in biofilms attaching onto anode graphite of cellulose-fed microbial fuel cells (MFCs). To identify their ecological roles, the present study isolated a corresponding bacterium (strain Mfc52) by direct plating of a biofilm suspension onto a solid medium containing glucose and ferric ion. Phylogenetic analysis revealed that this strain is deeply branched in the class Alphaproteobacteria and may represent a novel order. Strain Mfc52 fermented sugars and produced lactate, acetate, and fumarate, whereas ferric ion stimulated the growth on glucose. When an MFC was inoculated with this strain and supplemented with glucose, it fermented glucose and generated electricity by oxidizing organic acids produced from glucose. Electron micrographs showed that a fraction of cells in a liquid culture had prosthecae-like appendages that were abundantly observed in anode biofilm. These observations suggest that the bacterial population represented by strain Mfc52 shared an important niche in the cellulose-fed MFC, where it generated electricity by oxidizing intermediate metabolites from cellulose degradation. [ABSTRACT FROM AUTHOR]