Activation of Clostridium perfringens spores under conditions that disrupt hydrophobic interactions of biological macromolecules

Abstract

The effect of hydrophobic interactions on the activation of C. perfringens NCTC 8679 spores was examined by heating spores under conditions that modify the hydrophobic properties of biological macromolecules. After the activation treatment and a washing procedure, germination was determined by measuring the decrease in optical density of spores suspended in an enriched germination medium. Activation was inhibited for spores that were treated under conditions that strengthen hydrophobic interactions, i.e., a decrease in pH or the presence of structure-stabilizing neutral salts. Activation was enhanced by treatment under conditions that disrupt hydrophobic interactions, i.e., an increase in pH or the presence of urea, dibucaine, or denaturing neutral salts. A deactivation treatment with the antichaotropic salt (NH4)2SO4 reversed activation by the chaotropic salt CaCl2 and to a lesser extent reversed activation by sublethal heat (75 degrees C) or urea. Most treatments that enhanced activation increased spore injury at higher temperatures, which resulted in decreased germination. However, (NH4)2SO4 and a decrease in pH from 5.6 to 3.8, which inhibited activation, also favored injury. The results suggest that activation involves a conformational change of a spore protein(s) through weakening of hydrophobic molecular forces and that activation and injury occur at different spore sites.