Conjugation and transformation are both kinds of horizontal gene transfer that allow a cell to receive and recombine external DNA. Conjugation involves physical contact between two bacteria using a pilus, through which a copy of plasmid DNA is transferred from the donor (F+) cell to the recipient (F-) cell. Transformation, on the other hand, is simple uptake of naked DNA into a recipient cell from the environment. The DNA usually comes from the leftovers of a dead cell.
