The Earth's shallow subsurface results from integrated biological, geochemical, and physical processes. Methods are sought to remotely assess these interactive processes, especially those catalysed by micro-organisms. Using saturated sand columns and the metal reducing bacterium Shewanella oneidensis MR-1, we show that electrically conductive appendages called bacterial nanowires are directly associated with electrical potentials. No significant electrical potentials were detectable in columns inoculated with mutant strains that produced non-conductive appendages. Scanning electron microscopy imaging revealed a network of nanowires linking cells-cells and cells to mineral surfaces, "hardwiring" the entire length of the column. We hypothesize that the nanowires serve as conduits for transfer of electrons from bacteria in the anaerobic part of the column to bacteria at the surface that have access to oxygen, akin to a biogeobattery. These results advance understanding of the mechanisms of electron transport in subsurface environments and of how microorganisms cycle geologic material and share energy.


Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Bacteria; Microbiology; Microorganisms; Mineralogy; Minerals; Nanowires; Scanning Electron Microscopy; Bacterial Nanowires; Microbial Nanowires; Mineral Surfaces; Biogeochemistry; Bacterium; Electrical Conductivity; Electron; Microbial Activity; Microorganism; Bacteria (microorganisms); Shewanella Oneidensis MR-1

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 2007 American Geophysical Union (AGU), All rights reserved.

Publication Date

01 Sep 2007

Included in

Geology Commons