Multiply branched replicative intermediates in E. coli and bacteriophage lambda.

Multiple branched DNA fragments present in a fast sedimenting complex comprising a minute fraction of the E. coli genome have been isolated. Similar structures were also observed among bacteriophage lambda DNA replicative intermediates after infection of synchronized E. coli cells. These structures were found to be associated with the amino acid and thymidine starvation steps required for synchronization and originate either by initiation from secondary sites or by snap-back of daughter strands containing substantial single stranded regions in the vicinity of the growing point.