Post-replication repair of the heat-induced DNA injury in Deinococcus radiodurans.

Abstract

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 (30 μg/ml) or phenethyl alcohol (0.5%), inhibitors of DNA synthesis, the repair of single-strand DNA breaks was inhibited, and the restoration of growth and DNA synthesis during post-heating incubation was also inhibited completely. A recombination-deficient mutant strain (rec30) was more sensitive to heat than the wild type strain R1. When both the strains were heated at 55°C for 8 min, the survival fraction of R1 cells was nearly 100%, but that of rec30 cells was only approximately 0.01%. Though the breaks of DNA molecules induced by heating at 55°C for 8 min occurred in both rec30 cells and R1 cells, the DNA breaks 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. recombinat...