Molecular Nature of the Deoxyribonucleic Acid of a Thermosensitive R Factor, Rts1

The deoxyribonucleic acid of the thermosensitive R factor, Rts1, has been examined by the technique of sedimentation in alkaline sucrose, electron microscopy, and radiation target size. All these methods yielded a molecular weight of approximately 120 million for Rts1 deoxyribonucleic acid in Escherichia coli. Sedimentation analysis revealed that Rts1 deoxyribonucleic acid in Proteus mirabilis was also 120 million daltons. Rts1 did not segregate into E. coli minicells under the conditions where another smaller non-thermosensitive R factor could.