Minimal requirements for commitment to sporulation in Bacillus megaterium.

Commitment to sporulation was examined by means of both endotrophic sporulation and rejuvenation experiments. In both cases, a point of commitment to the completion of sporulation occurred at stage II. With 2 x 10(8) cells/ml, the process by which commitment occurred required 0.5 mm Mg(2+), 10.0 mm phosphate, and an energy source (minimum of 5.0 mm acetate). For completion of sporulation and formation of normal, heat-resistant refractile spores, 0.3 mm Ca(2+) was required. Except for this Ca(2+) requirement, the completion of sporulation after commitment was independent of the nature of the surrounding medium. Some aspects of the utilization of these required substances were examined.