Kinetics of DNA replication in bacteria with heterogeneous generation times

Abstract

Kinetics of DNA synthesis in bacteria which exhibit dispersion in the generation times of individual cells are calculated for a model in which each cell synthesizes DNA during its entire life-cycle. These kinetics are expressed as the amounts of DNA in each of three categories as a function of time. The categories represent original material, synthesized before a hypothetical transfer to medium in which newly synthesized DNA can be identified; hybrid material, representing the first stage of semiconservative replication, and fully new material, in which neither strand contains original material. The problem is solved by computer simulation of a cell population in exponential growth, with generation times distributed to produce varying amounts of heterogeneity. In addition we calculate the time course of emergence of transforming markers into hybrid and new DNA when a culture with all chromosomes initially aligned at the origin of replication is permitted to replicate in new medium.