Abstract
Induction of a Mu prophage in Escherichia coli Hfr strains lyosgenic for Mu cts62 leads to the generation of F' episomes. Each episome thus formed carries at least one copy of the Mu genome. These results suggest that integration of Mu is mandatory for the formation of the heterogeneous circles during the lytic cycle. The circles may be precursors for phage maturation.