Certain aspects of the pH dependence of triggering inBacillus megaterium spores

Abstract

Incubation of unactivatedBacillus megaterium 14581 spores in glucose, or in glucose plusl-alanine, at or below pH 3.6 resulted in germination arrested somewhere before onset of stainability. However, triggering continued at this reduced pH, and spores thus triggered were fully capable of completing the germination sequence in the absence of the germinants once the pH was neutralized. The same spores could be triggered either by a mixture of glucose andl-alanine or by a larger concentration of glucose alone. From this it was concluded that triggering results from an adequate stimulus which can be generated in different ways.l-alanine action in triggering has a pH profile distinct from that of glucose, suggesting that these two germinants have different receptor sites as well. At a level of acidity at which a weak glucose concentration triggered relatively few spores, a much larger fraction was found apparently distributed over a range of sub-triggering levels. Some of these could be made to trigger on transfer to a secondary reagent, or mixture of reagents, which by themselves are not very efficient germinants of the strain studied. The degree of additional triggering was found to depend on the nature of the complementary germinants, as well as on the pH at which glucose stimulated them. Evidence that spores may occupy stimulated states for finite lifetimes is presented and discussed.