F deoxyribonucleic acid transferred to recipient cells in the presence of rifampin.

When Escherichia coli F+ cells resistant to rifampin and streptomycin are mated with F- cells sensitive to the antibiotics, a large fraction of F factor deoxyribonucleic acid (DNA), which is transferred to the recipient cells in the presence of either of the antibiotics, can be recovered as covalently closed, circular double-stranded DNA, as in the control mating in the absence of antibiotic. Similar results were obtained in the presence of chloramphenicol or chloramphenicol plus rifampin. It is suggested that the transferred single-stranded F DNA can be converted to the covalently closed, circular double-stranded form in the absence of protein synthesis, and that rifampin-sensitive transcription is not required for the conversion.