Synchronization of bacteria by a stationary-phase method.

Cutler, Richard G. (University of Houston, Houston, Tex.), and John E. Evans. Synchronization of bacteria by a stationary-phase method. J. Bacteriol. 91:469-476. 1966.-Cultures of Escherichia coli and Proteus vulgaris have been synchronized, with a high percentage phasing, in large volumes and at high cell densities by a method which takes advantage of a tendency of cells to synchronize themselves when entering the stationary phase of growth. The method consists of growing the bacteria to an early stationary phase, harvesting them quickly under minimal conditions of stress, and inoculating them into fresh medium at a dilution of about sevenfold. Cellular division is then partially synchronized. Four-generation cycles of a high percentage of phasing are obtained by repeating this procedure on the partially synchronized culture. Deoxyribonucleic acid (DNA), ribonucleic acid (RNA), and protein analyses were made throughout all phases of the growth curve. Advantage has been taken of this method of synchrony to isolate selected segments of the bacterial genome in significant amounts. A working hypothesis to explain the synchrony suggests that the unfavorable conditions of growth as the bacteria near the stationary phase are detected by a decrease in the amino acid pool size, and that this results in a gradual decrease of DNA transcription activity through the inhibition of RNA polymerase by transfer RNA. The synchronizing method may be unique in producing cultures that grow both in cellular division and in genomic synchrony.