Hungry bacteria that can make toxic soil harmless

At military practice ranges across the country, the use of explosives has contaminated the soil with DNT, a product of the breakdown of TNT and a potential carcinogen. Some of the contamination is so vast that it's impractical to physically remove it. Enter the toxin-hungry bacteria Pseudomonas that have the ability to break down DNT. But the breakdown requires oxygen, keeping the bacteria close to the earth's surface and away from contamination deeper in the ground. Illinois Institute of Technology (IIT) biologists Ben Stark and Dale Webster are working to give the bacteria an advantage: the oxygen-bearing protein hemoglobin. Pseudomonas lacks the hemoglobin gene, but Stark and Webster have successfully spliced the hemoglobin gene from Vitreoscilla into Pseudomonas. (Dale Webster and his colleagues discovered bacterial hemoglobin in 1987.) The gene should help the bacteria grow, as well as supply extra oxygen for the crucial first step of DNT breakdown. Ultimately, the engineered bacteria would be infused into the ground and turn hazardous waste into innocuous chemicals. And with its oxygen boost, the engineered bacteria will be able to thrive at deeper levels. "This bioremediation approach may be the best way to get rid of toxic compounds such as DNT," said Stark. The U.S. Air Force Office of Scientific Research is funding the research with a $420,000 three-year grant.

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6/26/95