Transformation of Escherichia coli by R404 factor DNA and properties of the transformants.

Three r-determinants (Cb Cm Cf) out of eight present in R404 factor were transferred in transformation of Escherichia coli by the plasmid DNA isolated from minicells. The r-determinants acquired in this way formed the replicon tr404-1 and were untransferable by conjugation unless another self-transmissible plasmid was present in recipient. The evidences are presented in support of hypothesis that the transfer events consist in infection of transformant cells with sex factor, recombination between tr404-1 replicon and the sex factor and finally transfer of the new formed structure to the host cells of the sex factor.