Effect of Heat Treatment on the Germination of Bacterial Endospores

It has generally been believed that bacterial endospores were activated by beat treatment at considerably high temperature (about 80°C). Such treatment of the spores is, therefore, often called “heat activation”. In some particular cases, however, the germination of bacterial spores was sometimes found to be delayed by such a heat treatment. In order to ascertain whether the heat treatment does stimulate the germination of bac-terial spores or not, we observed in this work the germination of both heated and unheated spores of Bacillus subtilis under various conditions. The results obtained may be summarized as follows. (1) In the case of the freshly harvested spores, the germination was delayed by heat treatment under all the conditions employed; the heat treatment had always an inhibitory effect on the germination regardless of the compositions of sporulating and germinating media or the temperature used for the heat treatment. (2) The spores which had been stored at 0°C for more than 66 days were remarkably activated by the heat treatment at 80°C for 20 minutes; germination of the heated spores was more rapid than that of the unheated spores in the germination media which contained L-alanine in the concentration of higher than 1mM. These results suggest that the effect of heat treatment on the germination of spores of Bacillus subtilis essentially varies with the storage condition of the spores.