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The discovery of microalgae with an exceptional radiotolerance

​A new, highly radiotolerant microalga species has just been isolated from a cooling pool for spent nuclear fuel. After analyzing the properties of this unique species, researchers now foresee new strategies for bioremediation [1].

Published on 12 February 2013

The newly discovered Coccomyxa actinabiotis, a tiny unicellular alga, can resist a radiation dose of 20,000 Gy – 2,000 times the lethal human dose. This is the first eukaryotic organism [2] known to tolerate absorbing such high levels of ionizing radiation; until now, only bacteria such as Deinococcus radiodurans were thought to be capable of this. Researchers from the CEA-iRTSV in Grenoble have found that a period of two weeks is enough time for Coccomyxa actinabiotis to return to normal growth, following a radiation dose of 10,000 Gy. Another advantage of this microalga is that it concentrates radionuclides. This concentration turns out to be 10,000 more radioactive than the cooling pool water, as this species can accumulate most of the radionuclides present in the water, i.e. 80 – 100% of the silver, cesium, zinc, cobalt, uranium and carbon-14. This efficiency is comparable to that of physico-chemical processes conventionally used for decontamination.

Thus, the basis for a new idea: to exploit this alga for radioactive waste clean-up within (or exiting) nuclear facilities, or even following accidental contamination of the environment. The CEA and the Institut Laue-Langevin have put together a bioreactor pilot study to provide a proof of concept, which will optimize the bioremediation strategy. In addition, the researchers hope to elucidate the biochemical and genetic mechanisms that are used by Coccomyxa actinabiotis to withstand radiation and concentrate radionuclides.

[1] The application of cultures of living organisms (e.g. plants and bacteria) for the cleaning of polluted sites.

[2] Eukaryotes are composed of cells with a nucleus surrounded by their own membrane, within which the DNA is organized into chromosomes. In contrast, the unicellular prokaryotes (bacteria) lack this nucleus

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