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Abstract
SUMMARY: Synchronous cultures obtained by selection at division were used to investigate the occurrence of cold-sensitive stages during the division cycle of Escherichia coli (Îindâ). There are two such stages within the 50 min cycle: one (early) at 10 to 20 min and the other (late) at 40 to 45 min. Similar results were obtained from calculations based both on the age frequency distribution of cells in exponential growth and on the size of the populations which accumulate as a result of a single change of temperature. Times of about 17 and 44 min were found for the early and the late stages, respectively. It is concluded that the two-step doubling of E. coli k12 cultures synchronized by a single cold shock is due to two cold-sensitive stages in the division cycle.
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