from Eduardo A. Robleto, Holly A. Martin, Amber M. Pepper and Mario Pedraza-Reyes writing in Bacterial Spores: Current Research and Applications:
Endospore formation in the Bacilli has been used extensively as a proxy for cell growth and differentiation. Research that spans many years has revealed that endospore formation is a complex and elegant process that exquisitely coordinates the development of a dormant spore. The spore structure allows survival when nutrients and moisture are scarce. Once growth-conducive conditions are restored, the process of germination gives rise to vegetative cells. The cell differentiation program of sporulation is activated upon cessation of growth. Comparison of gene regulons activated during sporulation and stress survival suggest that the mode of regulation of endospore formation is well conserved between Bacilli and Clostridia.
Further reading: Bacterial Spores Related publications