OPTICAL DENSITY OF THE ENDOSPORE OF BACILLUS CEREUS AND ITS RELATION TO GERMINATION AND RESISTANCE

Publisher Website
Google Scholar
Abstract
The normal heat-resistant endospores of B. cereus appear bright when observed in dark contrast with the phase microscope. In a nutritive medium, and when the ambient temperature is favorable for germination, the endospores tend to turn dark and, simultaneously, their resistance to heat and drying drops to the vegetative level. In glucose-infusion media at 30[degree]C, 20 to 40% of the endospores undergo this change in less than 5 min. In the absence of nutritents and at supramaximal temperatures in the presence of nutrients, bright endospores have no tendency to change in appearance or in resistance. When endospores that had been in a nutritive medium at a supramaximal temperature are transferred to distilled water at a temperature suitable for germination, they tend to become dark and to acquire vegetative characteristics before the absorbed food material is completely removed. The importance of these observations in the study of spore resistance and their bearing on the survival of spore-forming bacteria are pointed out, germination is discussed, and the methods used in this study are described.