Horizontal DNA propagation is mediated by several mechanisms; bacterial conjugation is the most widespread and the one that contributes most to the horizontal gene pool in the prokaryotic world [7].
The promiscuity of bacterial conjugation goes beyond prokaryotes.
The ultimate example of this versatility is the DNA transfer system of Agrobacterium tumefaciens [38], mediated by a transfer machinery highly homologous to a Gram-negative conjugative apparatus [17], that efficiently transfers DNA into the nucleus of plant cells.
In addition, but only under laboratory conditions, conjugative DNA transfer has been observed from bacteria into yeast, plant and animal cells