Geobacter are the subject of intense investigation because they are useful agents in the bioremediation of groundwater contaminated with pollutants such as toxic and radioactive metals or petroleum. They also have the ability to convert human and animal wastes or renewable biomass into electricity. To carry out these processes, Geobacter must transfer electrons outside the cell onto metals or electrodes. This new research provides an explanation of how this can happen.
Previous studies in Lovley's laboratory demonstrated that 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 an atomic force microscope. They found the pili were highly conductive. Furthermore, when Geobacter was genetically modified to prevent it from producing pili, Geobacter could no longer transfer electrons.
“These results help us understand how Geobacter can live in environments that lack oxygen and carry out such unique phenomena as removing organic and metal pollution from groundwater,?Lovley said. Geobacter can live in the absence of oxygen because of its ability to transfer electrons outside the cell onto iron minerals, which are natural constituents o
Source:UMass Amherst News