RELATION BETWEEN THERMAL-RESISTANCE AND DPA CONTENT IN VARIANTS OF THE SAME STRAINS OF BACILLUS-STEAROTHERMOPHILUS SPORES

Rough and smooth variants of Bacillus stearothermophilus strains ATCC 12976 and 12980 were isolated. These variants showed morphologically d ifferent colonies. In both strains the rough variants were less heat-r esistant than the smooth ones, and their activation occurred in a shor ter time; on the other hand, their dipicolinic acid (DPA) content was higher. These results indicate that a relationship between higher DPA content and higher thermal resistance does not exist. Therefore, this evidence supports the hypothesis that DPA is not the determining facto r in the degree of spore heat resistance but that it could, instead, h ave a role in maintaining thermal resistance obtained by other means.