Induction of Sporulation during Chromosome Replication by Bacillus Cereus and Changes in Chromosomal Proteins of Cells that Sporulated

Synchronous chromosome replication was obtained in a culture of a temperature-sensitive mutant (ts-4) of Bacillus cereus growing in a rich medium at 45°C. At 10, 40, and 90 min from the start of chromosomal replication, samples of cells were transferred to a sporulation medium. After cultivation at 30°C for 20 hr, the sporulation rate was measured. The capacity of B. cereus ts-4 to sporulate was highest at 40 min after chromosome replication began, and had declined at 90 min. Other cells were cultured at 30°C for 120 min after the start of replication, and their chromosomes were prepared by treatment first with 10μg/ml N-acetylmuramidase SG and 2.5 mg/ml lysozyme, and later with 1% Briji 58 and 0.4% SDS. Patterns of two-dimensional electrophoresis of the chromosomal proteins from cells transferred at 10, 40, and 90 min were compared. The chromosomes of cells transferred at 40 min had greatly decreased amounts of 10 different proteins, but the amounts of three other proteins had increased. Some of these proteins seem to control the initiation of sporulation by B. cereus ts-4.