Synchrony of Division in Clonal Microcolonies of Escherichia Coli.

Hoffman, Heiner (New York University, New York, N.Y.), and Michael E. Frank. Synchrony of division in clonal microcolonies of Escherichia coli. J. Bacteriol. 89:513-517. 1965.-A common pattern of synchrony of division was found in 18 clonal microcolonies studied by means of time-lapse photomicrography. One of these is described in detail. Cell counts at 1-min intervals were carried into the 11th generation of a microcolony photographed for 5.25 hr. The counts indicated that an early synchrony of division occurred which apparently was gradually dissipated during the course of cultivation. However, when times of cell division for each generation were plotted, it became apparent that each generation conformed to a distribution curve which gradually changed in its characteristics from one generation to the next. The range of time during which the divisions occurred increased from 16 min in the 6th generation to at least 74 min in the 11th. Overlap between distribution curves increased from 3 min between the 7th and 8th generations, where it initially occurred, to at least 20 min between the 10th and 11th. Skewness of the distribution curve progressed from a negative value (-0.943) in the 5th generation to a positive value (+0.339) in the 10th. Genealogical identification of the first and last quarters of the cells to divide within a generation revealed, early in the course of cultivation, a cell subline which was dividing in a pattern of synchrony independent of the colony as a whole. The characteristics of this synchronous pattern, however, gradually progressed with each new generation toward those of the microcolony as a whole.