Microbial Ecology of Bacillus thuringiensis VI. Germination of Bacillus thuringiensis Spores in the Soil

To elucidate whether Bacillus thuringiensis spores germinate in natural soils, the population dynamics of vegetative cells and spores of B. thuringiensis in soils were studied using peptone-polymyxin medium and BTV medium, a selective medium for vegetative cells. B. thuringiensis spores were capable of germinating in sterilized soils but not in natural nonsterilized soils. B. thuringiensis vegetative cells inoculated into natural soils disappeared rapidly in 1-2 days. B. thuringiensis vegetative cells were able to form spores in antural soils, depending on the soil type. It is suggested that the spore is the only state in which B. thuringiensis persists in natural soils.