The iron-reducing bacteria Geobacter and Shewanella, as well as acetogenic, methanogenic, and iron-oxidizing bacteria have all been shown to perform extracellular electron transfer (EET) enabling electrical interactions between biofilms and the surface they live on. However, our understanding of the microbial electrical wiring that enables this non-natural connection is remarkably limited. Understanding electrode EET processes could result in leap-ahead technological advancements in applications including microbial electrosynthesis, bioremediation, microbial bioelectronics, and conductive materials derived from electric bacteria. Using a meta-omics and microbial electrochemistry approach we have expanded our understanding of thus far uncultivable electroautotrophs, bacteria presumed to “eat” electricity and use the energy gained to fix CO2. Metaproteomic and metatranscriptomic data supports the discovery of a previously uncharacterized electroautotroph from a marine biocathode microbial community referred to as Biocathode-MCL, which we have recently proposed as the candidate genus and species “Candidatus Tenderia electrophaga”. The electrical pathways we have uncovered in “Ca. Tenderia electrophaga” show that direct electron transfer may be possible through a series of c-type cytochromes spanning the cell outer membrane and periplasm as has been proposed for iron-oxidizing bacteria. Electrochemical measurements using an interdigitated electrode array and complimented by confocal Raman microscopy (CRM) indicating that long-range electron transfer (conductivity) through this biocathode biofilm is dominated by electron-hopping, presumably mediated by proteins of “Ca. Tenderia electrophaga”. Current efforts by the microbial electrochemistry group at the Naval Research Lab are focused on confirming the biochemical nature of the EET and conductive properties of the Biocathode MCL biofilm and intentionally engineering these traits into marine heterotrophic organisms for more precise electrical control of their cellular metabolism. Such efforts could lead to electrically driven microbial catalysis of precursor molecules for biofuels or biopolymers.

Electrical interactions between biofilms and surfaces

254th National Meeting (2017)

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