Germ erases toxic waste

Neutralizer: A bioengineered "superbug" can help to clean up highly radioactive sites.

Medicine & Science

December 01, 2003|By Robert S. Boyd | Robert S. Boyd,KNIGHT RIDDER/TRIBUNE

Scientists are working to perfect a "superbug" to help clean up toxic wastes at thousands of radioactive sites worldwide.

The mighty microbe - nicknamed "Conan the Bacterium" - combines the genes of two bacteria to perform a job neither could do on its own.

The composite creature "can live quite happily in an environment with 1 million times the radiation a human cell could tolerate," Department of Energy Secretary Spencer Abraham said at a news conference last month.

Conan works because its radiation-resistant bacterium (Deinococcus radiodurans) shelters the twosome from lethal rays, while the partner (Pseudomonas putida) uses its native ability to render poisons in soil or water harmless.

"Our scientists have shown that it is possible to combine Conan's radiation-resistance properties with the capabilities of other microbes," Abraham said. "We are ready to turn it to our own uses."

The DOE estimates there are 3,000 sites contaminated with 40 million cubic yards of toxic wastes - many of them radioactive. "Some of these waste sites are really hot - they're cookin'!" said Michael Daly, a biologist at the Uniformed Services University of the Health Sciences in Bethesda.

Daly and genome wizard Craig Venter, founder of the Institute for Genomic Research in Rockville, determined the complete sequence of the Deinococcus genome in 1999. Daly continues to work on practical applications of the modified microbe in his laboratory.

One application under development might help cancer patients resist the unpleasant side effects of radiation therapy.

"It's very exciting," Daly said in a telephone interview. "There are more things to come that I can't talk about yet."

Conan can break down the chemical structure of toluene - an ingredient in explosives such as TNT that contaminate many Energy Department waste sites - leaving only carbon dioxide and water. "You can't get less toxic than that," Daly said.

Conan also works on mercury, dangerous pesticides such as chlorobenzene, and PCBs, carcinogenic compounds formerly used in manufacturing.

Although Conan's technology has been proved in the lab, field tests have been blocked by objections from environmentalists.

"Some people were appalled that we generated radiation-resistant microbes that are potentially going to vaporize mercury and put it in the atmosphere," Daly said.

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