[Detection of plasmids in the cells of E. coli CK]

Superspiralized coiled plasmide DNA were found in cells E. coli CK. One of plasmides pEco CK-1 had a size 21.2 micron that corresponded to molecular mass 43.7 megadaltons, another plasmide pEco CK-2 with the size 14.2 micron had a molecular weight 29.2 megadaltons. Effective restriction was observed in cross titration using phage PBV-I.CK for E. coli strains carrying R II plasmide and phage PBV-I.R II for E. coli CK cells. The data obtained suggest that the Eco CK type with DNA of host specificity is distinct from hsp II type due to presence of R II and N-15 plasmides.