Findings: Attractive bacteria

April 11, 2003

Getting intimate with bacterial attractions could help clean contaminated groundwater for drinking, writes Natasha Gilbert.

According to US researchers, efforts to put bacteria to work in polluted groundwater, as is done with oil spills, have previously been thwarted. Scientists assumed that the problem was caused by the attraction of negatively charged polymers (strings of sugar molecules) on the surface of bacteria to positively charged iron particles in the soil. These, it was thought, helped bacteria to stick around in nutrient-rich environments, preventing them from following the pollutant's trail downstream.

But when graduate student Richard Campen and his supervisor, James Kubicki of the department of geosciences at Penn State University, took a closer look, they found that uncharged polymers also present on the surface of bacteria adhered to iron particles in a similar way.

The findings indicate that charged attractions might not be causing the stickiness. "Our experiments suggest that the neutral polymers may be responsible for adhesion," Mr Campen told The THES . "The charged polymers would play a different role."

The bacteria might be able to change the shape of their charged polymers by shifting the distribution of charge along their length, he said. This would change the shape of the uncharged polymers - altering their ability to interact with surfaces and hence their adhesive strength.

Mr Campen said this explanation was a more energy-efficient way for the bacteria to stick around in good environments or make themselves less likely to stick in nutrient-poor environments. According to Mr Campen, this new understanding could provide a means to control how bacteria adhere in soils. Bacteria that use harmful chemical compounds as food could then be injected into the ground "and the rest of the clean-up would take care of itself".

The findings were announced last week at the 225th American Chemical Society meeting in New Orleans.

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