HEAT, HYDROGEN-PEROXIDE, AND UV RESISTANCE OF BACILLUS-SUBTILIS SPORES WITH INCREASED CORE WATER-CONTENT AND WITH OR WITHOUT MAJOR DNA-BINDING PROTEINS

Spores of a Bacillus subtilis strain with an insertion mutation in the dacB gene, which codes for an enzyme involved in spore cortex biosynt hesis, have a higher core water content than wild-type spores. Spores lacking the two major alpha/beta-type small, acid-soluble proteins (SA SP) (termed alpha(-)beta(-) spores) have the same core water content a s do wild-type spores, but alpha(-)beta(-) dacB spores had more core w ater than did dacB spores. The resistance of alpha(-)beta(-), alpha(-) beta(-) dacB, dacB, and wild-type spores to dry and moist heat, hydrog en peroxide, and UV radiation has been determined, as has the role of DNA damage in spore killing by moist heat and hydrogen peroxide. These data (i) suggest that core water content has little if any role in sp ore UV resistance and are consistent with binding of alpha/beta-type S ASP to DNA being the major mechanism providing protection to spores fr om UV radiation; (ii) suggest that binding of alpha/beta-type SASP to DNA is the major mechanism unique to spores providing protection from dry heat; (iii) suggest that spore resistance to moist heat and hydrog en peroxide is affected to a large degree by the core water content, a s increased core water resulted in large decreases in spore resistance to these agents; and (iv) indicate that since this decreased resistan ce (i.e., in dacB spores) is not associated with increased spore killi ng by DNA damage, spore DNA must normally be extremely well protected against such damage, presumably by the saturation of spore DNA by alph a/beta-type SASP.