gamma-Ray-induced DNA damage and repair in Methanosarcina barkeri

The capacity of the mesophilic archaeon, Methanosarcina barkeri (DSM 804) f or DNA double strand break repair following Co-60-gamma irradiation was inv estigated. The genome (1.9 Mb) of Methanosarcina barkeri was largely fragme nted and was found to be repaired on incubation in medium under anaerobic c onditions at 37 degreesC for 4 h. To get an insight into its repair process a set of inhibitors were used. The methanogenesis inhibitor, bromoethane-s ulfonate showed partial inhibition of repair in Methanosarcina barkeri but not in Escherichia coli or human peripheral blood mononuclear cells. The Me thanosarcina barkeri cells could also partially repair the DNA damage in a non-nutrient medium. Arabinosine-CTP, a nucleoside analogue and a polymeras e inhibitor, completely inhibited repair in this archaeon. Arabinosine-CTP did not affect DSB (double-strand break) repair in human peripheral blood m ononuclear cells but completely inhibited repair in Escherichia coli (a bac terium). The involvement of polymerase indicates recombination to be the un derlying mechanism in DSB repair of Methanosarcina barkeri. 3-Aminobenzamid e, a poly (ADP-ribose) polymerase inhibitor, completely inhibited repair in this archaeon as well as in eukarya but not in Escherichia coli showing th e involvement of poly (ADP-ribose) polymerase in the DSB repair of Methanos arcina barkeri. (C) 2000 Academic Press.