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It would sicken or kill other organisms, but this mycorrhizal fungus consumes depleted uranium and leaves it in a less mobile form.

Credit: Marina Fomina et al. (Current Biology 18)

Fungus Could Be a Fix for Uranium Pollution

By Phil Berardelli
ScienceNOW Daily News
5 May 2008

Modern warfare has introduced a new and insidious type of pollutant to battlegrounds in the Middle East and Europe: depleted uranium. The compound consists of the nonexplosive uranium-238 that remains after the fissile uranium-235 has been extracted for making nuclear explosives and other purposes, plus a touch of titanium. Depleted uranium's high density makes it extremely useful for armor and munitions. But when shell collides with armor, fine particles scatter, so the military use of depleted uranium has left soil and water tables in battlegrounds polluted. Although less radioactive than natural uranium, the depleted form is nonetheless toxic and as hazardous as lead or mercury.

Researchers at the University of Dundee in the United Kingdom examined whether certain natural fungi could help clean up uranium from sites in the Balkans and Iraq. They knew from past studies that some types of fungi can ingest toxic substances without apparent harm. So in laboratory experiments, they fed depleted uranium to so-called mycorrhizal fungi, which usually live in the roots of plants, taking carbon from the plants and furnishing nutrients in return. Within a few months, the team reports tomorrow in Current Biology, the mycorrhizal fungi had surrounded and chemically transformed the depleted uranium to a stable phosphate compound. Because this compound isn't a nutrient, it doesn't work its way into the food chain.

Even better, this transformational ability of fungi "would work for pollution with any--depleted or not--metallic uranium and its corrosion products," says environmental microbiologist and lead author Marina Fomina. "Our findings could also be applied to cleaning up contaminated liquid wastes, metal leaching, and recycling and recovery," she says.

Soil ecologist John Dighton of Rutgers University in New Brunswick, New Jersey, calls the findings "great work" and an important step forward in identifying how fungi can slow the buildup of uranium in the environment. Understanding the role of fungi in radioactive and heavy-metal interactions in the soil is "important from many perspectives," he adds, particularly their impact on human health and the environment.

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