Triggering in unactivated Bacillus megaterium spores

Abstract

The kinetics of triggering in unactivated spores of Bacillus megaterium ATCC 14581 were studied over a wide range of concentrations of the germinant β-D-glucose. At all but the lowest glucose concentration investigated, the rate of triggering decreased continuously on increasing duration of exposure to the germinant, this decrease being faster than exponential. Our results suggest that both triggering and its inhibition are alternative outcomes of the interaction of the germinant with the spores. At sufficiently dilute glucose concentrations the triggering curve is sigmoidal with unactivated spores, but is exponential if the spores have been previously heat shocked. In the absence of an initial lag interval on triggering, the observed decrease in the sample lag time by either heat activation or on increasing the glucose concentration in unactivated spores makes it necessary to consider that the effects of these two forms of stimulation are not limited to the triggering event.