Synchronized replication of Mycobacterium tuberculosis.

When Mycobacterium tuberculosis was grown in Tween-albumin broth without any agitation, the bacilli replicated in the upper, oxygen-rich portion of the medium at a rate that was just balanced by the rate at which the bacilli settled toward the bottom of the tube. When the organisms that accumulated in the sediment were suspended and diluted into fresh medium, they exhibited synchronous replication. The bacilli initiated ribonucleic acid synthesis immediately upon suspension, but marked deoxyribonucleic acid synthesis was not apparent until after the first cellular division was completed, about 14 h after suspension.