Immense volumes of radioactive waste, generated from nuclear weapons production during the Cold War, were disposed directly to the ground. The current expense of remediating these polluted sites is driving the development of alternative remediation strategies using microorganisms. The bacterium Deinococcus radiodurans is the most radiation resistant organism known and can grow in highly irradiating (greater than 60 Gray/h) environments. Numerous microorganisms (e.g., Pseudomonas sp.) have been described, and studied in detail, for their ability to transform and degrade a variety of organic pollutants (e.g., toluene), present at many radioactive DOE waste sites. Detoxification of the organic toxins at these sites is an important goal in remediating or stabilizing contaminated sites as well as preventing their further dissemination. The aim of this project is to engineer strains of D. radiodurans that are capable of degrading organic/aromatic hydrocarbons present in radioactive mixed waste sites - sites that contain mixtures of toxic organic compounds, radionuclides and heavy metals. Conventional bioremediating organisms are unable to survive at many of these sites because of their sensitivity to radiation. Generally, microorganisms are sensitive to the damaging effects of ionizing radiation, and most of the bacteria currently being studied as candidates for bioremediation are no exception. For example, Pseudomonas sp. is very sensitive to radiation (more sensitive than E. coli) and is not suited to remediate radioactive wastes. Therefore, radiation resistant microorganisms that can remediate toxic organic compounds need to be found in nature or engineered in the laboratory to address this problem.
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