Induction of sporulation during synchronized chromosome replication in Bacillus subtilis

Synchronous chromosome replication was obtained in a culture of Bacillus subtilis temperature-sensitive mutants growing in a rich medium. At intervals during this replication, samples of cells were transferred to a poor medium to induce sporulation. The results show that the capacity of B. subtilis for induced sporulation reaches a peak about 15 min after chromosome replication has begun. This capacity then declines rapidly, but can be restored by initiating a new round of deoxyribonucleic acid replication. The possibility is discussed that sporulation can be induced only when the chromosome replication fork is passing through a stage 0 operon and that this may be located in the cysA-sul(R) region of the chromosome.