Ultrastructural changes associated with activation and germination of Bacillus cereus T spores.

The ultrastructural changes occurring during defined stages of the transition of dormant Bacillus cereus T spores into heat-sensitive forms were investigated. The coat of the heat-activated spores displayed conspicuous striations across its middle layer. Electron microscopy of thin sections of heat-activated spores revealed the presence in the spore of a layer consisting of hexagonally oriented subunits. It was demonstrated that the subcoat region, but not the cortex, disappears rapidly during germination of B. cereus T spores. The fibrous structures apparently associated with the spore coat remain virtually unchanged during the entire course of activation and germination.