Role of DNA repair in Bacillus subtilis spore resistance

Wet-heat or hydrogen peroxide treatment of wild-type Bacillus subtilis spores did not result in induction of lacZ fusions to three DNA repair-related genes (dinR, recA, and uvrC) during spore outgrowth. However, these genes were induced during outgrowth of wild-type spores treated with dry heat or UV. Wet-heat, desiccation, dry-heat, or UV treatment of spores lacking major DNA-binding proteins (termed alpha-beta- spores) also resulted in induction of the three DNA repair genes during spore outgrowth. Hydrogen peroxide treatment of alpha-beta-spores did not result in induction of dinR- and rerA-lacZ but did cause induction of uvrC-lacZ during spore outgrowth. Spores of a recA mutant were approximately twofold more UV sensitive and approximately ninefold more sensitive to dry heat than were wild-type spores but were no more sensitive to wet heat and hydrogen peroxide. In contrast, alpha-beta- recA spores were significantly more sensitive than were alpha-beta- spores to all four treatments, as well as to desiccation. Surprisingly, RecA levels were quite low in dormant spores, but RecA was synthesized during spore outgrowth. Taken together, these data (i) are consistent with previous suggestions that some treatments (dry heat and UV with wild-type spores; desiccation, dry and wet heat, hydrogen peroxide, and UV with alpha-beta- spores) that kill spores do so in large part by causing DNA damage and (ii) indicate that repair of DNA damage during spore outgrowth is an important component of spore resistance to a number of treatments, as has been shown previously for UV.