Independence of F replication and chromosome replication in Escherichia coli

Data are presented which show that F replication is not coupled to any stage of the replication cycle of the host chromosome or to cell division, and is probably not related to surface area. It is also shown that the initiation mass of F increases progressively as the growth rate increases, the number of copies of F per unit of mass falling by half between doubling times of 0.8 and 2.7 generations per hour. It is further shown that the presence of an F particle does not influence the initiation mass of the chromosome.