Non-Chromosomal Antibiotic Resistance in Bacteria, III: Isolation of the Discrete Transfer Unit of the R-Factor R1*

AUTOR(ES)

Cohen, Stanley N.

RESUMO

A covalently-closed circular DNA species, banding at a buoyant density of ρ = 1.709 g/cm3 in CsCl, has been identified in antibiotic-sensitive colonies of E. coli strain AB2463 (rec A-) after mating with a Proteus mirabilis strain that carries the R-factor, R1. This plasmid, which represents a stable segregant of R1 that has lost all of the drug resistance determinants present on the parent R-factor but which has retained its ability to be transferred by conjugation, fulfills the functional definition of the R-factor transfer unit (RTF).

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