The roles of DNA repair by apurinic/apyrimidinic (AP) endonucleases alone, and together with DNA protection by alpha/beta type small acid-soluble spore proteins (SASP), in Bacillus subtilis spore resistance to different types of radiation have been studied. Spores lacking both AP endonucleases (Nfo and ExoA) and major SASPwere significantly more sensitive to 254-nm UV-C, environmental UV (>280 nm), X-ray exposure, and highenergy charged (HZE)-particle bombardment and had elevated mutation frequencies compared to those of wild-type spores and spores lacking only one or both AP endonucleases or major SASP. These findings further implicate AP endonucleases and alpha/beta type SASP in repair and protection, respectively, of spore DNA against effects of UV and ionizing radiation
