Post-replication Repair of the Heat-induced DNA Injury in Deinococcus radiodurans

概要

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Single- and double-strand breaks in deoxyribonucleic acid (DNA) of Deinococcus radiodurans R1 cells caused by heating at 55°C for 8 min were rejoined by post-heating incubation in nutrient borth. In the presence of novobiocin (30μg/ml) or phenethyl alcohol (0.5%), inhibitors of DNA synthesis, the repair of single-strand DNAbreaks was inhibited, and the restoration of growth and DNAsynthesis during post-heating incubation was also inhibited completely. A recombinationdeficient mutant strain (rec30) was more sensitive to heat than the wild type strain Rl. Whenboth the strains were heated at 55°C for 8 min, the survival fraction ofRl cells was nearly 100%, but that of rec30 cells was only approximately 0.01%. Though the breaks of DNAmolecules induced by heating at 55°C for 8 min occurred in both rec30 cells and Rl cells, the DNAbreaks in the former cells were not restored during post-heating incubation in nutrient broth. Therefore, it can be concluded here that post-replication repair i.e. recombination repair, contributes to the repair during post-heating incubation of heat-induced DNAinjury of D. radiodurans cells.