The formation of endospores in bacteria is typically studied under conditions where growth is exhausted, such as in mineral salt solutions or nutrient-free media. However, a new approach emerged in 1961 when it was observed that spores are continuously formed in exponentially growing cultures of *Bacillus megaterium* and *B. subtilis* in a mineral-glucose medium. This phenomenon, where the number of spores increases at a constant rate equal to the growth rate of the total population, suggests that the probability of a cell committing to sporulation is influenced by the intracellular concentration of nitrogen-containing catabolites. The study investigates the factors affecting the sporulated fraction (ρ) in growing cultures of *B. subtilis*. The results indicate that the probability of sporulation is influenced by the nature and concentration of both carbon and nitrogen sources. For example, the probability is higher with NH4Cl as the nitrogen source and glucose as the carbon source compared to other combinations. The probability also varies with the concentration of the carbon source and is independent of temperature. The authors propose that catabolites, which are nitrogen-containing compounds, directly or indirectly repress the expression of all sporulation genes. This hypothesis is supported by the observation that certain amino acids and intermediates of the tricarboxylic acid cycle significantly decrease the sporulated fraction while increasing the growth rate only slightly. The repression is not an all-or-none phenomenon but reflects the intracellular concentration of the repressing metabolite, which depends on the rate of anabolic reactions and repressor formation. The study also discusses the identification of the key enzyme(s) affected by catabolites and the coordinated repression of all sporulation genes. It suggests that the sporulation genes may belong to multiple distinct operons, and sequential induction might be involved in their coordinated expression. The findings provide insights into the regulation of sporulation and the role of catabolites in this process.The formation of endospores in bacteria is typically studied under conditions where growth is exhausted, such as in mineral salt solutions or nutrient-free media. However, a new approach emerged in 1961 when it was observed that spores are continuously formed in exponentially growing cultures of *Bacillus megaterium* and *B. subtilis* in a mineral-glucose medium. This phenomenon, where the number of spores increases at a constant rate equal to the growth rate of the total population, suggests that the probability of a cell committing to sporulation is influenced by the intracellular concentration of nitrogen-containing catabolites. The study investigates the factors affecting the sporulated fraction (ρ) in growing cultures of *B. subtilis*. The results indicate that the probability of sporulation is influenced by the nature and concentration of both carbon and nitrogen sources. For example, the probability is higher with NH4Cl as the nitrogen source and glucose as the carbon source compared to other combinations. The probability also varies with the concentration of the carbon source and is independent of temperature. The authors propose that catabolites, which are nitrogen-containing compounds, directly or indirectly repress the expression of all sporulation genes. This hypothesis is supported by the observation that certain amino acids and intermediates of the tricarboxylic acid cycle significantly decrease the sporulated fraction while increasing the growth rate only slightly. The repression is not an all-or-none phenomenon but reflects the intracellular concentration of the repressing metabolite, which depends on the rate of anabolic reactions and repressor formation. The study also discusses the identification of the key enzyme(s) affected by catabolites and the coordinated repression of all sporulation genes. It suggests that the sporulation genes may belong to multiple distinct operons, and sequential induction might be involved in their coordinated expression. The findings provide insights into the regulation of sporulation and the role of catabolites in this process.