GENETIC RECOMBINATION BETWEEN THE RESISTANCE TRANSFER FACTOR AND THE CHROMOSOME OF ESCHIERICHIA COLI.

Ginoza, Herbert S. (National Aeronautics and Space Administration, Moffett Field, Calif.), and Robert B. Painter. Genetic recombination between the resistance transfer factor and the chromosome of Escherichia coli. J. Bacteriol. 87:1339-1345. 1964.-Genetic instability for high-level streptomycin and chloramphenicol resistance was observed in several strains of Escherichia coli infected with the resistance transfer factor (RTF) episome. The altered site was always found on the chromosome, and the resistance characteristics were similar to, if not identical with, the corresponding determinant found on the episome. The high-level drug resistance phenotype was ascribed to two separate loci acting cooperatively within the host. The instability phenomenon had been attributed to a genetic exchange mechanism in which the chromosome copies the drug-resistance information from the episome, thus giving rise to a diploid homogenote for this segment. In a reciprocal exchange system, the tetracycline-resistance marker on the chromosome was shown to recombine with the RTF episome lacking this information.