Electric bacteria
us researchers have found how some microorganisms can clean groundwater and produce electricity from renewable resources. The ability owes to a highly electrically conductive, tiny structure called microbial nanowire that the scientists at the University of Massachusetts Amherst discovered in Geobacter.
The nanowires are only 3-5 nanometres thick (20,000 times finer than a human hair), but quite durable and more than a thousand times as long as they are wide. A nanometre is one-billionth of a metre. The discovery may also have applications in nanotechnology. The findings of the team, led by microbiologist Derek R Lovley, were published in Nature (June 23, Vol 435, No 7045).
Such long, thin conductive structures are unprecedented in biology, said Lovley, who is also credited with the discovery of Geobacter in 1987. These microbes have been found useful in the bioremediation of groundwater contaminated with toxic and radioactive metals or petroleum. They also have the ability to convert human and animal wastes or renewable biomass into electricity. Geobacter are anaerobic bacteria (living without oxygen) that use metals to gain energy the way humans and other organisms use oxygen.
Previous studies in Lovley's lab showed Geobacter produces fine, hairlike structures, known as pili, on just one side of the cell. Lovley's team speculated that the pili might be miniature wires extending from the cell that would permit Geobacter to carry out its unique ability to transfer electrons outside the cell onto metals and electrodes. This was confirmed in a study in which microbiologist Gemma Ruegera teamed with physicists Mark T Tuominen and Kevin D McCarthy to probe the pili with the high resolution atomic force microscope. They found the pili were highly conductive. Further, when Geobacter was genetically modified to prevent it from producing pili, the bacteria could no longer transfer electrons.
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