Replication of DNA in bacteria with heterogeneous generation times

The relation between DNA replication and cell division in steady-state dividing bacterial cultures is examined with respect to the heterogeneity of generation times which is observed in such populations. Two simple, extreme hypotheses are considered: (1) DNA replication is heterogeneous in rate, occupying the entire generation time in each cell; and (2) DNA replication occupies a constant time, the remainder of the life cycle of the cell being a rest period with no DNA synthesis. The distribution of replication points is calculated, and from this the marker frequency function and the fraction of DNA synthesized in the absence of initiation of replication. The two alternative hypotheses lead to theoretically distinguishable predictions. Available experimental evidence, although not conclusive, favors the first hypothesis.