Microgermination of Bacillus cereus spores.

The biphasic nature of germination curves of individual Bacillus cereus T spores was further characterized by assessing the effects of temperature, concentration of germinants, and some inorganic cations on microgermination. Temperature was shown to affect both phases of microgermination as well as the microlag period, whereas the concentration of l-alanine and supplementation with adenosine exerted a significant effect only on the microlag period. The germination curves of individual spores induced by inosine were also biphasic and resembled those of spores induced by l-alanine. High concentrations (0.1 m or higher) of calcium and other inorganic cations prolonged both phases of microgermination, particularly the second phase, and had a less pronounced effect on the microlag period. The second phase of microgermination was completely inhibited when spores were germinated either in the presence of 0.3 m CaCl(2) or at a temperature of 43 C; this inhibition was reversible. Observations on the germination of spore suspensions (kinetics of the release of dipicolinic acid and mucopeptides, loss of heat resistance, increase in stainability, decrease in turbidity and refractility) were interpreted on the basis of the biphasic nature of microgermination. Dye uptake by individual spores during germination appeared also to be a biphasic process.