ASSOCIATION OF R6K PLASMID REPLICATIVE INTERMEDIATES WITH FOLDED CHROMOSOME OF ESCHERICHIA-COLI

When E. coli strain CSH50(R6K) is lysed so as to preserve the folded chromosome structure, 9 of the 11 R6K molecules maintained/chromosomal equivalent cosediment with the host nucleoid on a neutral sucrose gradient; the remaining 2 plasmids sediment at their normal rate. When cells are briefly labeled with [3H]thymidine, the majority of plasmid replicative intermediates and nascent mature plasmids are found in the plasmid subpopulation that cosediments with host folded chromosomes. Plasmid replication probably occurs in a restricted cellular locus, perhaps even while in association with its host''s folded chromosome.