FIG. 2.

Growth curve (closed symbols) and sporulation frequencies (open symbols) of B. subtilis 168 cultivated in minimal medium (circles) and in minimal medium supplemented with 0.2% CAA (diamonds). The number of spores per milliliter of culture was determined as the number of heat-resistant (80°C for 30 min) CFU on Luria-Bertani plates, and the number of viable cells was determined as the total number of CFU (before heat treatment). Sporulation frequencies were defined as the percentage of heat-resistant CFU. Four independent experiments,which gave comparable results, were carried out.