SHIFT OF CELL-AGE DISTRIBUTION PATTERN IN THE LATER PHASES OF ESCHERICHIA COLI CULTURE

Abstract

Escherichia coli K-12 E64 was grown in a synthetic medium containing succinate or glucose as the carbon source and changes in the cell age distribution pattern occurring in the aged culture was examined employing biochemical and cytological methods including autoradiography.
Following the log phase, the growth proceeded linearly for a short period and then the stationary phase ensued. In the linear phase, cells gradually ceased to synthesize DNA leaving protein and RNA synthetic activities still active, although the rate was fairly reduced. These processes in the linear phase were accompanied with a decrease in DNA content per cell to a certain low level and the decrease in nuclear number toward one and two nuclei per cell. In the late linear phase the cultures seemed to be synchronized at least partially at the post-division stage. It was indeed demonstrated that when the aged cultures were diluted with fresh media, a characteristic synchronous cell division occurred after about one generation time.