Cooperative effects of daunorubicin and actinomycin D on the sporulation of Bacillus subtilis.

Actinomycin D allowed 3.6% of spore formation and 4.9% of dipicolinic acid synthesis of control cultures when added at 0.4 microM at late stage (T6.5) during sporulation process of Bacillus subtilis although the drug inhibited sporulation almost completely when added at log phase and early stages. Daunorubin added at log phase, on the other hand, did not inhibit either growth and sporulation of the bacteria up to a concentration of 2.9 microM. The joint use of both antibiotics at late stages decreased the levels of spore formation and the synthesis of dipicolinic acid allowed by the use of actinomycin D alone to 0.9% and 2.1% respectively, and also inhibited the synthesis of spore coat protein in a cooperative manner.