Timing and genetic regulation of commitment to sporulation in Bacillus subtilis.

Sporulation in Bacillus subtilis is a simple developmental system involving the differentiation of two cell types called the prespore and the mother cell. The process is induced by nutrient deprivation and culminates with the formation of a mature spore, which is released by lysis of the mother cell. We have studied commitment to sporulation with several different assays. The results indicate that commitment occurs soon after the formation of the asymmetrically positioned division septum that separates the prespore and the mother cell. This is earlier than the previously postulated point of commitment, prespore engulfment by the mother cell. Commitment coincides approximately with activation of the early prespore- and mother-cell-specific sigma factors, sigma(E) and sigma(F).