The present invention is directed to an in vivo method of transferring DNA from a donor cell to a recipient cell. In a specific embodiment, the method comprises a highly efficient process of bacterial mating. In a preferred embodiment, selection for a recombinant plasmid against a parent host plasmid and donor plasmid is based on recircularization of the host plasmid by its recombination with a gene of interest such that it is now no longer cleaved by a restriction enzyme expressed in the recipient cell.