Fungi to fight 'toxic war zones'

Fungi could help clean up toxic war zones, scientists at a Scottish university have discovered.

Dundee University researchers have found evidence that fungi can "lock" depleted uranium into a mineral form.

This would make it more difficult for the heavy metal - used in armour-piercing shells - to find its way into plants, animals or the water supply.

The fungal-produced minerals are capable of long-term uranium retention, the scientists say.

Prof Geoffrey Gadd, from the university's College of Life Sciences, said: "This work provides yet another example of the incredible properties of micro-organisms in effecting transformations of metals and minerals in the natural environment.

DEPLETED URANIUM Has a reduced proportion of isotope Uranium-235 Less radioactive than natural uranium and very dense Military uses include defensive armour plating, armour-penetrating ordnance Can be inhaled as dust or ingested in contaminated food and water near impact sites

"Because fungi are perfectly suited as biogeochemical agents - often they dominate the biota in polluted soils, and play a major role in the establishment and survival of plants through their association with roots - fungal-based approaches should not be neglected in our attempts to deal with metal-polluted soils."

The testing of depleted uranium ammunition and its recent use in Iraq and the Balkans had led to contamination of the environment with the unstable metal, said Prof Gadd, who heads the Division of Molecular and Environmental Biology at Dundee.

Depleted uranium differs from natural uranium. It is the by-product of uranium enrichment for use in nuclear reactors or nuclear weapons and is valued for its very high density.

Although less radioactive than natural uranium, depleted uranium is just as toxic and poses a threat to people.

In the new study, the researchers found that free-living and plant fungi can colonise depleted uranium surfaces and transform the metal into uranyl phosphate minerals.

Professor Gadd said that while they likely still posed some threat, "the fungal-produced minerals are capable of long-term uranium retention, so this may help prevent uptake of uranium by plants, animals and microbes. It might also prevent the spent uranium from leaching out from the soil."

The research, published in the journal Current Biology, concludes that the discovery could lead to uranium-polluted soils eventually being brought back into use.

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