Roles of DacB and Spm proteins in Clostridium perfringens spore resistance to moist heat, chemicals and UV radiation

Department of Biomedical Sciences, College of Veterinary Medicine and Department of Microbiology, College of Science, Oregon State University, Corvallis, OR 97331; and Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030

^* To whom correspondence should be addressed. Email: sarkerm{at}oregonstate.edu.

	Abstract

Clostridium perfringens food poisoning is caused mainly by enterotoxigenic type A isolates that typically possess high spore heat-resistance. Previous studies have shown that /-type small, acid-soluble proteins (SASP) play a major role in the resistance of Bacillus subtilis and C. perfringens spores to moist heat, UV radiation and some chemicals. Additional major factors in B. subtilis spore resistance are the spore's core water content and cortex peptidoglycan (PG) structure, with the latter properties modulated by the spm and dacB gene products and the sporulation temperature. In current work we have shown that the spm and dacB genes are expressed only during C. perfringens sporulation and have examined the effects of spm and dacB mutations and sporulation temperature on spore core water content and spore resistance to moist heat, UV radiation and a number of chemicals. The results of these analyses indicate that for C. perfringens SM101: (i) core water content and probably cortex PG structure have little if any role in spore resistance to UV and formaldehyde, presumably because these spore's DNA is saturated with /-type SASP; (ii) spore resistance to moist heat and nitrous acid is determined to a large extent by core water content and probably cortex structure; (iii) core water content and cortex PG cross-linking play little or no role in spore resistance to hydrogen peroxide; (iv) spore core water content decreases with higher sporulation temperatures resulting in more moist heat resistant spores; and (v) factors in addition to SpmAB, DacB and sporulation temperature play roles in determining spore core water content and thus spore resistance to moist heat.