Stimulation of Germination of Unactivated Bacillus cereus Spores by Ammonia

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Abstract
Inclusion of NH3 in germinant mixtures containing L-alanine and inosine stimulated germination of unactivated B. cereus spores at rates equal to those obtained using heat-activated spores without NH3. D-Alanine had little effect on germination of heat-activated spores, but severely inhibited germination of unactivated spores in the presence of NH3. NH3 did not replace the requirement for either L-alanine or inosine; all 3 compounds were required for rapid germination. Kinetic analysis suggested that the functions of NH3 and L-alanine were more closely related than the functions of NH3 and inosine. With rate-saturating concentrations of L-alanine and inosine, germination rates showed saturation kinetics for NH3 with a Km for NH4Cl of 5 mM. Comparisons of the effects of salts, amines and pH on germination rates suggested that NH4OH rather than NH4+ was the rate-limiting form of NH3. In comparisons of various strains of B. cereus, stimulation of germination by NH3 occurred in all cases, although spores of most soil isolates germinated more rapidly than B. cereus T spores in the absence of NH3.

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