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. 1970 Oct;104(1):340–344. doi: 10.1128/jb.104.1.340-344.1970

Studies on Resistance Transfer Factor Deoxyribonucleic Acid in Escherichia coli

Richard P Silver a,1, Stanley Falkow a
PMCID: PMC248219  PMID: 4919749

Abstract

A variant of the derepressed R factor, R1, which does not contain any of the drug resistance markers, and represents, in large part, the resistance transfer factor (RTF) was studied in Escherichia coli. RTF deoxyribonucleic acid (DNA) was specifically labeled in a female cell after conjugation. Physical characterization of the molecule showed that RTF possessed an average molecular weight of 50 × 106 daltons and a buoyant density of 1.709 g/cm3. By comparison to R1, we calculate that the region of DNA carrying the drug resistance genes is therefore about 20% of the R1 molecule and has a buoyant density of approximately 1.716 g/cm3. These results support the hypothesis that the single species of R-factor DNA observed in E. coli represents a composite of the 1.709 and 1.716 g/cm3 replicons seen in Proteus.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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