Variation of generation times in Escherichia coli populations: its cause and implications.

The cell cycle of Escherichia coli contains a period of indeterminate length that reflects a stochastic reaction, beginning at some time after a round of chromosome replication, and ending before the cell divides. Although the chemical nature of this reaction is not known, the time of its onset and the single statistical 'half-life parameter' required for its quantitative description have been measured previously. Here it is shown that this parameter implies the distribution of generation times and the age distribution, as well as the distributions of replication initiation and termination ages; these distributions are derived from this half-life parameter for exponentially growing populations of E. coli. It is also shown that the stochastic reaction affects the results and interpretation of any experiments involving synchronous growth of bacteria.