Superbug for digesting atomic waste

Researchers have developed a bacterial strain of Deinococcus radiodurans that can detoxify both mercury and toluene at nuclear waste sites.

provided by Nature Biotechnology

he trouble with most nuclear waste sites is that they usually contain a nasty mess of heavy metals, organic chemicals, and radioactive isotopes. Now, scientists have exploited the hardy properties of the world's most radiation-resistant bacterium to create a super bug that can tackle all these contaminants at the same time. Unlike other pollution-eating bugs that quickly die as a result of radioactivity exposure at atomic dumps, the new bug is resistant to radiation and can be engineered with the enzyme machinery to tackle both toxic metals and organics.

Michael Daly and his colleagues had already shown that their hardy test bacterium -- Deinococcus radiodurans can clean up the fraction of organic waste present at radioactive sites. But many atomic waste sites also contain other toxins, such as heavy metals, as well as organic chemicals and radioactivity. What is needed is a versatile bacterium that can not only tackle organic chemicals, but also toxic metals, in a radioactive environment.

Daly's team set about this task by creating four different strains of D. radiodurans in which a set of foreign genes for converting toxic mercury into its less harmful elemental form were placed in the bacterium, either on circles of DNA (plasmids) or integrated into the bacterial chromosome. All four strains were able to grow in the presence of radiation and ionic mercury, and capable of detoxifying mercury those strains containing many copies of the genes being somewhat more efficient mercury vaporizers. The team then went on to develop a strain that can detoxify both mercury and toluene, a poisonous organic solvent, demonstrating that different sets of gene can be slotted into D. radiodurans to provide varied pollution-fighting attributes. Future efforts are likely to attempt to integrate several other bioremediation functions into the bacterium, creating a kind of superbug capable of making a variety of types of waste less hazardous.

Author: Dr. Michael J. Daly, Dept. of Pathology Rm. B3153, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, MD 20814-4799; (301) 295-3750; fax: (301) 295-1640;