Radiation Resistance of Spores of <i>Bacillus subtilis</i> and <i>B. stearothermophilus</i> at Various Water Activities

Abstract

S ummary . The radiation resistance of spores of Bacillus subtilis and B. stearothermophilus was determined under anoxic conditions in water vapour and in aqueous solutions of glucose and glycerol at various water activities. In water vapour, resistance of both kinds of spores increased slightly with decreasing water activity ( a w ). In glycerol solutions, a phase of rapid increase in resistance with decreasing a w was followed by a slower increase on further reduction of a w . This second phase was almost parallel to the water vapour curve, which, however, showed considerably lower resistance. The initial phase of rapid increase in resistance was also observed in glucose solutions.