Relation of Maximum Growth Temperature to Resistance to Heat

Abstract

Heat-tolerance of microorganisms is directly related to the max. temp. of growth. Data from the literature are brought together which indicate the relationship to be true for bacterial cells. Spores originating from Clostridium with the higher maximum growth temp. are the more resistant kinds within the genus. Conidia of spp. of Aspergillus are generally more heat-tolerant than those of Penicillium spp. which as a group have the lower maximum growth temp. Original data on the heat-resistance of spores of 73 strains of mesophilic aerobic spore-forming bacteria collected under controlled conditions are presented. Within the genus Bacillus the relationship holds for endospores and 3 groups of species are separable with respect to spore resistance in relation to maximum growth temp. Exceptions are noted and their existence interpreted to mean that factors in addition to those which determine maximum temp. of growth are involved in thermal resistance.