Electrical microbes

Bacteria used to clean up contaminated land and to generate electricity from organic wastes produce electrically conductive ‘nanowires’ to transfer electrons from inside their cells to metal particles, according to researchers from the University of Massachusetts Amhurst. ‘This completely changes our concept of how microorganisms can handle electrons,’ comments research leader Derek Lovley.

The microbes are members of the Geobacter family, which is the subject of much study because of their ability to clean up groundwaters contaminated with toxic and radioactive materials. They can also generate electricity from human or animal waste, or other organic materials. Lovley’s team had previously found that the bacteria produce fine hairlike fibres, known as pili, on one side of their cells. Speculating that these might be the conduit for the bacteria’s electron flow, the team tested the pili with an atomic force microscope, and confirmed that they were indeed highly electrically conductive.

The pili are only 3-5nm wide and 3-5µm long, but are durable. ‘Such long, thin conductive structures are unprecedented in biology,’ Lovley says. The structures are likely to be useful in the design of small electronic devices, he says, as they are likely to be easier and cheaper to produce than laboratory-derived nanowires made of silica, carbon or metals.

According to Aristedes Patrinos of the US Department of Energy, which funds Lovley’s research, the discovery will also have environmental applications. The nanowires ‘may enable a microbial community in a contaminated waste site to form mini-power grids,’ he says, which ‘could provide new approaches to using microbes to assist in the remediation of DoE sites; to support the operation of mini-environmental sensors; and to nano-manufacture in novel biological ways.’