Bacteria fibres offer electronics and medical potential

Bacteria naturally found in the soil could be the source of electrically conductive nanowires that could be used in compact electronic devices, sensors, and even in devices that could generate alternative fuels from natural sources. The wires, which are produced by genetic modification, are smaller even than those that can be made by industry using current methods. Moreover, they do not require harsh chemical processes or pollutants in the manufacture.

The research was carried out by microbiologists at the University of Massachusetts Amherst, sponsored by the US Office of Naval Research, and led by Dr Derek Lovley. The team started with a microbe called Geobacter sulferreducens, which naturally produces conducting fibres made from proteins, that connect the bacterium to particles of iron oxide in the ground that support its growth. The current that it carries is too small to be useful for technology, but it is still measurable.

The conductivity of fibres is believed to stem from their structure, where the amino acids that make up the proteins are arranged so that their unsaturated regions with free electrons line up. To improve the conductivity, Lovley’s team genetically modified the bacteria to replace to the natural amino acids with tryptophan, an amino acid commonly found in the proteins that make up muscle fibres. Tryptophan is highly efficient at transporting electrons. "We arranged the amino acids to produce a synthetic nanowire that we thought might be more conductive," said Lovley. "We hope that Geobacter would still produce nanowires and it might double their conductivity."