Underground Power Lines: Bacterial Nanowires and Extracellular Electron Transfer through Porous Media

Microorganisms significantly contribute to complex biogeochemical processes in saturated and unsaturated soils and subsurface sediments. Energy required to run these reactions is principally extracted from reduced organic compounds while electron acceptors range from oxygen to solid phase iron and manganese oxides.

Availability of electron acceptors is commonly limited in anaerobic subsurface environments. Dissolved electron acceptors, such as oxygen and nitrate, are limited by low concentrations while solid phase electron acceptors, such as iron and manganese minerals, are typically limited by surface area or crystallinity. Most bacteria studied to date produce electrically-conductive appendages called bacterial nanowires in response to electron acceptor limitation. Dissimilatory metal reducing bacteria apparently use nanowires to transfer electrons from bacteria to solid phase minerals that serve as electron acceptors. This presentation will provide a status report of our progress toward investigating the presence and reactivity of bacterial nanowires produced by microorganisms in soils and subsurface sediments.