Fig. 4.

Sporulation frequency of the spo0A mutant and ACE-complemented derivatives. The various strains were cultivated in CBMS medium at 37 °C and samples taken at 0, 24, 48, 72, 96 and 120 h, subjected to a heat shock (80 °C for 10 min) before plating at serial dilutions on CBM agar and incubated for 48 h. The number of colonies was counted and heat resistant Colony Forming Units per ml (CFU/ml) was calculated. Estimates were undertaken in triplicate. The detection limit of the assay is 50 CFU/ml, so no counts were recorded with the spo0A mutant control (not shown) or at 0 h with any of the strains