Bacillus subtilis(B. subtilis) cells were placed in various environmental conditions to study the effects of aeration, water activity of the medium, temperature, pH, and calcium content on spore formation and the resulting properties. Modification of the sporulation conditions lengthened the growth period of B. subtilis and its sporulation. In some cases, it reduced the final spore concentration. The sporulation conditions significantly affected the spore properties, including germination capacity and resistance to heat treatment in water (30 min at 97 degrees C) or to high pressure (60 min at 350 MPa and 40 degrees C). The relationship between the modifications of these spore properties and the change in the spore structure induced by different sporulation conditions is also considered. According to this study, sporulation conditions must be carefully taken into account during settling sterilization processes applied in the food industry.