Turbidimetric Measurement on Synchronized Salmonella typhimurium Cultures

Abstract

SYNCHRONIZATION of cellular and nuclear division in Salmonella typhimurium populations at densities of 1–4 × 10⁷ cell/ml. has been reported previously^1,2. Two systems for obtaining such synchronization were described, both systems employing temperature shifts between 25° and 37°. In the first system the temperature of a culture which had been growing for ten generations at 25° was raised to 37°. In the period between 5 and 10 min. following the rise in temperature, 80–90 per cent of the population underwent nuclear division as observed cytologically³, and as inferred from the interaction of the cells with a temperate bacteriophage. On the other hand, cellular division, as measured by colony counts, was delayed for 20–25 min., at which time it took place at an increased rate, finally re-establishing the exponential growth of the culture at the normal 37° rate (see Fig. 1).