All known living things harvest high-energy electrons from hydrocarbons for power. Those creatures which reside in oxygen rich environments pass these waste electrons to oxygen while those that live near geothermal vents use sulfur as their dustbin.
The bacteria pictured above, however, have access to neither. They live in minimal-sulfur soil at a depth where oxygen is unavailable. Instead, they pass their low-energy electrons to metals, readily available conductors in the earth. The idea that a metallic element may be substituted for something as “fundamental” to life as oxygen is food for the imagination. Beyond this, however, is an even more contentious concept. As you can see from the image, these bacteria produce nanoscale structures resembling wires. Furthermore, it has been demonstrated that these filaments conduct electricity (ref. 1). The researchers who demonstrated this fact believe that the bacteria are using their nano-wires to transport their electrons over long distances to the surface oxygen, creating a current source in the dirt.
This claim is by no means proven, but it is intriguing that the suggestion hasn’t even been considered until now. Also, the implications of an electrically connected community of bacteria are significant. Microorganisms have presented many examples of behaviors normally thought to be reserved to higher animals, and if the authors responsible for this work turns out to be true, studying the dynamic interactions of these communities has the potential to teach us about systems of electrically coupled cells like our brains. Taking speculation to the extreme, one might ask whether these creatures could constitute a biological-battery, yielding electricity for our own use.
1. Y. A. Gorby et al. (2006) Electrically conductive bacterial nanowires produced by Shewanella oneidensis strain MR-1 and other microorganisms Proc. Natl Acad. Sci. USA Vol. 103, pp. 11358–11363
2. Jestin JL, Kaminski PA. (2004) Directed enzyme evolution and selections for catalysis based on product formation. J Biotechnol. 113(1-3):85-103