Some bacterial transposons can be exchanged among many different species, usually carried by plasmids. Other transposed pieces of DNA can be inverted at one place in one species, to turn on or off the regulation of a gene. An example of such a site-specific transposition event is the flagellar gene regulation catalyzed by hin recombinase. They rarely exchange two entire genomes. Bacteria commonly exchange small pieces of genome, a few genes at a time, through transformation, transduction, or conjugation.
Transformation is the uptake of DNA from outside the cell.
Only a single strand is taken up, through a special protein complex in the cell membrane. Transformation occurs at extremely low frequency, but with large populations of bacteria, it offers a significant route for genetic transfer. This rare event results in a phage delivering only bacterial DNA to the next host. The DNA then recombines homologously, replacing the host allele. A shuttle vector is a plasmid engineered in the test tube to contain an ori site for bacteria, and an ori site for animal or plant cells.