"Such long, thin conductive structures are unprecedented in biology," said Derek Lovley of the University of Massachusetts Amherst. "This completely changes our concept of how micro-organisms can handle electrons, and it also seems likely that microbial nanowires could be useful materials for the development of extremely small electronic devices."

Lovley discovered Geobacter in 1987 at the bottom of the Potomac River in Washington DC, US. The bacteria, which are anaerobic, live in aquatic sediments and soils worldwide. The organisms respire by transferring electrons to material outside the cell, for example iron (III) oxides. This means they can be used to clean up groundwater contaminated with pollutants such as toxic and radioactive metals or petroleum.

The bacteria grow hair-like structures that are 3-5 nm wide and up to 20 µm long from one side of their cells. Lovley and colleagues tested these pili with an atomic force microscope with a conductive tip. They found that the structures were highly conductive - they believe that the pili provide an electrical connection between the cell and the surface of iron (III) oxides.

Harvesting pili from Geobacter cultures could provide a relatively cheap and simple way of producing nanowires. What’s more, the researchers reckon it would be possible to genetically modify the pilin structure or composition to create nanowires with different functionalities.

The scientists reported their work in Nature.