Regulation of the Initiation of Endospore Formation in Bacillus subtilis

Under certain environmental conditions, cells of the bacterium Bacillus subtilis can initiate a developmental process leading to the formation of dormant endospores. Much of the work on sporulation in B. subtilis has focused on several key questions such as What are the environmental conditions that control sporulation? The authors describe some of the regulatory circuits that control the initiation of sporulation and the conditions that influence the activity of the regulatory factors. The responses of the gram-positive soil bacterium B. subtilis to changing nutrient conditions have been studied extensively. Regulatory mechanisms exist to help ensure that cells do not initiate sporulation unless it is likely that they will be able to complete the process successfully. spo0A and spo0H encode transcription factors that are required for the initiation of sporulation. Both spo0A and spo0H are required for asymmetric division and for transcription of the genes required for establishing cell-type-specific gene expression. The genes controlled by Spo0A that are involved in formation of the axial filament and the polar FtsZ rings are not known. Extracellular and intracellular signals are generated by nutrient deprivation, cell density, DNA replication, DNA damage, glucose metabolism, the tricarboxylic acid (TCA) cycle, and chromosome-partitioning proteins. Understanding both the signals that regulate these pathways and the organization of the pathways into networks regulating gene expression will contribute significantly to an integrated view of the interplay among cell physiology, gene expression, adaptation, and development.