Glass formation and dormancy in bacterial spores

Differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR ) techniques were used to obtain evidence whether a glassy state exists wit hin fully hydrated dormant Bacillus subtilis spores. DSC thermograms of hyd rated dormant spores contained two major transitions; one at similar to 60 degrees C assigned to be associated with the initial 'activation' stage for germination, and the other at -120 degrees C assigned to be associated wit h the 'inactivation' process (i.e. killing of the spores). The peak at simi lar to 60 degrees C had characteristics which were all consistent with at l east some region of the compartmentalised structure of fully hydrated dorma nt spores being in a glassy state. Solid (CPMAS) and liquid state (SPMAS) m obility resolved C-13 NMR spectroscopy studies on the calcium dipicolinic a cid (CaDPA) resonances, which are only present in the central protoplast of bacterial spores, showed it to be present in an amorphous solid-like envir onment. The DSC and NMR results were both found to be consistent with the h ypothesis that the dormancy of bacterial spores is due to at least the cent ral protoplast region being maintained in a low moisture content glassy sta te.