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GEOPHYSICAL RESEARCH LETTERS, VOL. 34, L17305, doi:10.1029/2007GL030426, 2007

Microbial nanowires: Is the subsurface “hardwired”?

Dimitrios Ntarlagiannis

Environmental Engineering Research Centre, School of Planning, Architecture and Civil Engineering, Queen's University Belfast, Belfast, UK


Estella A. Atekwana

Boone Pickens School of Geology, Oklahoma State University, Stillwater, Oklahoma, USA


Eric A. Hill

Biological Sciences Division, Microbiology Group, Pacific Northwest National Laboratory, Richland, Washington, USA


Yuri Gorby

J. Craig Venter Institute, La Jolla, California, USA


Abstract

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.

Received 19 April 2007; accepted 31 July 2007; published 12 September 2007.

Keywords: self potential; nanowires; biogeophysics.

Index Terms: 0925 Exploration Geophysics: Magnetic and electrical methods (5109); 5109 Physical Properties of Rocks: Magnetic and electrical properties (0925); 0416 Biogeosciences: Biogeophysics; 0463 Biogeosciences: Microbe/mineral interactions.

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Citation: Ntarlagiannis, D., E. A. Atekwana, E. A. Hill, and Y. Gorby (2007), Microbial nanowires: Is the subsurface “hardwired”?, Geophys. Res. Lett., 34, L17305, doi:10.1029/2007GL030426.