Fig. 2.

Structure of the spore showing the different compartments. The innermost compartment, the core, contains the DNA and is filled with small acid-soluble proteins that saturate the DNA and protect it and all the other components present in the cytoplasm in a largely dehydrated state. The spore core is surrounded by two membranes sandwiching a specialized peptidoglycan called cortex keeping the water activity relatively low. The spore coat consists of two layers and is composed of about 70 different proteins. Pathogenic and some saprophytic Bacilli possess an additional layer called exosporium consisting of a paracrystalline basal layer and a hair-like nap. A thin section electron micrograph showing a spore with its exosporium has been presented [108]