Restriction map of the antibiotic resistance plasmid R1 drd-19 and its derivatives pKN102 (R1drd-19B2) and R1drd-16 for the enzymes BamHI, HindIII, EcoRI and SalI

Abstract

The conjugative R plasmid R1drd-19, mediating antibiotic resistance to ampicillin (Ap), chloramphenicol (Cm), kanamycin (Km), streptomycin (Sm) and sulfonamides (Su) was mapped using the restriction endonucleases BamHI, HindIII, EcoRI and SalI. BamHI generates 5 fragments (A-E) with molecular weights between 46×10⁶ dalton (representing mainly the RTF) and 0.25×10⁶ dalton, and HindIII 8 (A-H) between 42×10⁶ dalton (representing the main part of the RTF) and 0.1×10⁶ dalton. EcoRI recognises 17 sites and produces fragments (A-Q) with molecular weights between 11.7 and 0.1×10⁶ dalton. SalI yields 7 fragments (A-G) of 16.5 to 2.0×10⁶ dalton. A physical map was constructed from fragments obtained by partial digestion of R1drd-19 with one restriction enzyme, by double and triple digestion of the DNA with two or three enzymes with and without isolation of individual bands from preparative gels. In addition the restriction patterns of several mutants of R1drd-19 were compared with it. Evidence is presented which indicates that the derivatives of R1 investigated are generated by extende deletions, namely the copy mutant pKN102 which has lost the Km resistance, R1 drd-16, which has lost all resistances other than Km and the Km^s derivative of R1drd-16, which represents the pure RTF. The map of R1drd-19 is remarkably different from those of R100 and R6-5. Its molecular weight was estimated to be 62.5 Md. The circular fragment order for BamHI is: A-C-B-D-E, for HindIII: A-D-C-B-F-H-E-G, for EcoRI: A-C-K-B-F-J-O-D-H-L-G-P-Q-N-I-E-M-and for SalI A-B-C-D-G-F-E.