Thermal analysis of the spores of Bacillus cereus with special reference to heat activation

Abstract

The heat activation of bacterial spores was studied by means of differential thermal analysis in the temperature range 30–110 °C using the spores of Bacillus cereus. The thermogram showed three endothermic peaks at 56, 95, and 103 °C with one exothermic peak at 105 °C during the heating process. The spore coat separated from the native spores also showed a peak at 56 °C on its heating thermogram. The peak at 56 °C was reversible for both native spores and the spore coat. It was suggested that this peak at 56 °C might be related to the heat-activation process that takes place in the spore-coat region. It seems that the peak is due to the denaturation or the structural change of the spore-coat protein that might facilitate either the permeation of germination stimulators or the release of some germination inhibitor into or out of the spores.