Heat Injury of Bacillus subtilis Spores at Ultrahigh Temperatures

Abstract

The following three criteria indicated that Bacillus subtilis A spores were injured, but not completely inactivated, by ultrahigh temperature treatment. (i) Significant reductions in survivors were observed when spores were enumerated with a standard medium but not when the medium contained added CaCl 2 and sodium dipicolinate. (ii) After a damaging heat treatment, more survivors were enumerated with the standard medium after incubation at 32 C than at 45 C, which was opposite to the result with untreated or slightly heated spores. (iii) Apparent numbers of survivors increased during the initial period of 3 C storage when enumerated with the standard medium at 45 C. No injury was evident when survivors were enumerated at either incubation temperature with the medium containing added CaCl 2 and sodium dipicolinate. Heat activation of the spores did not significantly influence the appearance of heat injury. The data suggested that the heat injury occurred in a germination system which was required in the absence of CaCl 2 and sodium dipicolinate.