Recovery of ionizing-radiation damage after high doses of gamma ray in the hyperthermophilic archaeon Thermococcus gammatolerans
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The recently discovered hyperthermophilic and radioresistant archaeon Thermococcus gammatolerans is of great interest to compare and contrast the impact of its physiology on radioresistance and its ability to repair damaged chromosomes after exposure to gamma irradiation with radioresistant bacteria. We showed that, in contrast to other organisms, cell survival was not modified by the cellular growth phase under optimal growth conditions but nutrient-limited conditions did affect the T. gammatolerans radioresistance. We determined the first kinetics of damaged DNA recovery in an archaeon after exposure to massive doses of gamma irradiation and compared the efficiency of chromosomal DNA repair according to the cellular growth phase, nutrient availability and culture conditions. Chromosomal DNA repair kinetics showed that stationary phase cells reconstitute disrupted chromosomes more rapidly than exponential phase cells. Our data also revealed that this radioresistant archaeon was proficient to reconstitute shattered chromosomes either slowly or rapidly without any loss of viability. These results suggest that rapid DNA repair is not required for the extreme radioresistance of T. gammatolerans.
KeywordsThermococcus gammatolerans Archaea Hyperthermophile Radioresistance DNA repair kinetics
The LGA laboratory is supported by the CNRS and the Université Paris-Sud XI. A. Tapias was the recipient of an ATER-Université Paris-Sud XI position in Molecular Biology. C. Leplat is supported by a doctoral fellowship of the Ecole Doctorale GCDE Paris- Sud XI. Authors are specially grateful to J. Battista (Lousiana State University, USA) for fruitful discussions. We thank P. Forterre and E. Marguet for their help in the use of the anaerobic chamber and M. DuBow for help with English. We also thank G. Baldacci and V. Favaudon (Institut Curie, Orsay) for access to the Cs137 Gamma irradiation source. Authors are grateful to anonymous reviewers for their questions and suggestions to improve the quality of the manuscript.
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