Population heterogeneity in the resistance of aerobic spores to ethylene oxide.

The resistance of bacterial spores to lethal agents has long been studied not only as an aspect of applied microbiology but also as part of the general problem of the mechanism of resistance. An important consideration in the analysis of mechanisms is the sensitivity of measurement techniques with respect to variable factors. The usual methods for measuring the resistance of spores to a lethal agent such as ethylene oxide are based on the ability of the spores to germinate and grow on nutrient agar or broth. Neither the survivor-curve method nor the qualitative endpoint method, for example, can distinguish between the effect of ethylene oxide on spore germi-nation and its effect on the development of the germinated cell. Further, it might be expected that these effects would be influenced by the heterogeneity of the spore population reflected either in the spores' resistance to ethylene oxide or in their pattern of breaking dormancy and germinating. The experiments reported here were undertaken to analyze the relation between heterogeneity and some of the factors involved in the resistance of certain strains of bacterial spores to ethylene oxide.