Spore Germination and Outgrowth

This chapter focuses on spore germination principally as it is understood in Bacillus subtilis. The protease that initiates small acid-soluble spote proteins (SASP) hydrolysis during spore germination is discussed. While SASP degradation may be slower than cortex degradation, the latter event is not necessary for SASP hydrolysis. Spore outgrowth begins after spore germination, but in a spore population these two events overlap to a significant degree. Given the unique aspects of spore germination, it seems logical that there be some gene products involved uniquely in spore germination. The necessity for spore cortex hydrolysis for completion of normal spore germination and the unique aspects of spore cortex structure have focused attention on the possible involvement of one or more cortex lytic enzymes (CLEs) as playing a key role in spore germination. While spore outgrowth seems likely to utilize pathways and gene products needed for vegetative growth, although with perhaps a bit of outgrowth-specific regulation, it is clear that spore germination has a number of unique aspects. However, the mechanism and regulation of spore germination are far from being understood. The hydrolysis of a large amount of spore core protein early in spore germination indicates that a protease must be active at this time. This protease, termed the germination protease (GPR), is specific for its SASP substrates, which it cleaves one to three times within a highly conserved amino acid sequence.