A harmless soil bacterium, which can survive high-level exposures to gamma radiation, is being developed to clean up land contaminated with radioactive waste, experts heard today (Wednesday 12 September 2001) at the bi-annual meeting of the Society of General Microbiology at the University of East Anglia.
US government researcher Dr. Michael Daly of the Uniformed Services University of the Health Sciences, Bethesda, Maryland says "Until recently there have been no effective biological methods to treat highly radioactive contaminated sites because most known species are very radiation sensitive. We have found that the harmless soil bacterium Deinococcus radiodurans can survive a dose of 17,000 Gy, as well as grow in the presence of chronic high-level radiation (60 Gy/hour). For comparison, exposure to just 5-10 Gy is lethal to a human."
Now the US scientists have modified D. radiodurans to contain genes used to remove heavy metals from soil and break down toxic chemicals like toluene to carbon dioxide and water. The bacterium was modified successfully to express an assortment of toxin-degrading genes from other organisms using a combination of traditional genetic engineering and recent genomic information.
Immense volumes of radioactive waste, generated from the production of nuclear weapons in the USA, were disposed directly to the ground. This led to an amount of contaminated land equivalent to 1 metre of soil covering 10,000 football fields. A multitude of chemicals can be detected in the soil including radionuclides such as Uranium; heavy metals like mercury and lead; and toxic organic compounds, for example toluene.
Dr Michael Daly says “Deinococcus is a highly versatile biological system which will likely be used in the future to stabilize environments polluted by a wide range of toxic radioactive and organic chemicals and prevent them from escaping into the environment. This method could provide an effective alternative to conventional soil treatments such as incineration, landfill or soil-washing using large amounts of solvent.”
◊A public release from Society for General Microbiology in September 2001, viewed from biologyonline.com.