Media dependence of commitment in Bacillus subtilis

Abstract

At some time during sporulation development, cells of Bacillus subtilis develop a commitment to continue sporulation even after addition of or dilution into a fresh nutrient. The extent of commitment was measured by the titer of spores produced at the time at which the original culture sporulated maximally. Since newly formed spores of B. subtilis soon germinate in the replenished medium, the measurement of their titer, especially of heat-resistant spores, gave low values. This problem was avoided by the germination-delaying effect of methyl anthranilate (1 mM) when added together with the fresh nutrients. In a given culture, the titer of committed cells was then independent of the method by which it was measured, i.e., by the phase-bright, octanol-resistant, or heat-resistant spore titer. The time of commitment depended on the type of nutrient added. Commitment occurred earlor casein hydrolysate. The rates at which non-metabolizable amino acid analogues or the 14C from an amino acid mixture were taken up by the cells increased toward the end of growth and later declined. This decline occurred slowly and was only weakly correlated with the commitment time of an analogous amino acid.