COLUMBUS, Ohio -- Researchers here have isolated a previously unrecognized type of bacterium that can naturally degrade a chemical herbicide found in drinking water supplies in many cities around the country.

The compound, called atrazine, is used to kill weeds in corn, sugarcane, pineapple and other crops and is the most widely used herbicide in the country. It has become a concern of the Environmental Protection Agency, said Samuel Traina, a professor of natural resources at Ohio State University.

"In many cities, atrazine concentrations in drinking water

periodically approach about half of the maximum contaminant level allowed by the EPA," Traina said. "There's supposedly a large safety factor built into that maximum level allowed, but whenever you start to approach that level, people become concerned."

Traina and Olli Tuovinen, a professor of microbiology at Ohio State, headed the study of the organism, the first known naturally occurring single bacteria that can degrade atrazine.

Atrazine is a member of a class of herbicides called triazenes. The bacteria identified by the researchers are also

capable of degrading other triazene herbicides, and could be utilized in regions of the country where other triazene herbicides are more commonly used.

The bacteria were isolated from pesticide-contaminated soil at an agricultural experiment station in Ohio. These kinds of bacteria are relatively common in soil, but usually not in densities sufficient to degrade high levels of atrazine.

"The interesting thing about this organism is that it uses both the carbon and the nitrogen found in the atrazine," he said. "So it can really utilize a large percentage of the total atrazine molecule."

Tuovinen said parts of atrazine that are not used by these bacteria are likely degraded by other organisms in the soil.

Although the organism has only been studied in a laboratory, Traina said he believes it could be effective in removing atrazine from contaminated water supplies. The researchers are looking into ways to use the organism in water treatment plants, but Traina said this needs further study.

Cities with contaminated drinking water currently use granulated activated carbon to remove atrazine from the water. In some instances, the carbon is then collected and dumped at a landfill. By using the bacteria to do the same task, Traina said cities might save money and landfill space.

Another possible use of the organism is to remove pesticides from heavily contaminated soil. Pesticide mixing areas at agricultural sites are often layered with soil exposed to years of triazene and other chemical spills and need decontamination.

"If the soil from these sites had to be removed, it could be very expensive," Traina said. "And since many of these sites are owned by small businesses, the cost of doing this might be more than the value of the business." Using the organism to decontaminate the area could be more cost effective, he added.

Researchers plan to continue their study of the organism, looking at its genetic makeup and other biodegradative capabilities. "We want to see if the gene that allows it to degrade atrazine might be in other organisms in the soil," Tuovinen said.

The research was published in the January edition of Applied and Environmental Microbiology.

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Contact: Samuel Traina, (614) 292-9037; or Olli Tuovinen, (614) 292-3379

Written by Kelli Whitlock, (614) 292-9475