Bioremediation of polluted radioactive environments

Human society has been rapidly evolving industrially and with new technologies there is also a big problem; generation of waste and pollutants. Besides the problem of industrial waste discard, a lot of important industrial processes generate waste by accident or intrinsic to the production steps and those may not be purified at all, possibly contaminating soil, water and/or air.

Decontamination of soil and waste can have an enormous cost when using physical or chemical removal methods. However bioremediation can be cost-effective, eco-friendly and safer. Bioremediation can be defined as the use of microbes with one or more species in the process to turn toxic compounds into a less toxic form by treating contaminated areas.

To use bioremediation in radioactive areas, there is the need to use a microorganism that is resistant to radiation itself as in an extreme contaminated site like Chernobyl reactors the level of radiation can reach 20,000 grays and the lethal dose for humans are close to just 10. The most promising microorganism is the Deinococcus radiodurans species that have been isolated in canned meat irradiated with 4000 gray y-radiation in 1956 by Anderson et al. It is now known that this species can outstand 5000 gray without reduction of bacterial viable population and it’s also been studied for over 50 years making it a great target to radiation bioremediation studies.

This bacteria has been manipulated genetically with the use of plasmids to include more resistance to some metals that it is not naturally resistant. One example is the addition of merA locus from Escherichia coli using recombinant DNA technology which confers the D. radiodurans the ability to transform Hg(11) into the less toxic and volatile form Hg(0) while also conferring resistance to it. The bioremediation of the radioactive elements like uranium include the biotransformation of these into an insoluble form that precipitates or by immobilising the radioisotope in biological structures.

The possibility of genetically engineering this species and others that are radioresistant gives rise to the possibility of introduction of genes that generates not only resistance to other compounds but also the ability to detoxify organic compounds, toxic metals and other substances in radioactive environments, bringing the bioremediation of these areas one step closer.

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