actaully it occurs all the time. This swapping of genetic material among prokaryotes (bacteria) is analogous to sexual reproduction in eukaryotes (US). This is how bacteria confer survival genetic material from mutations. It occurs very commonly with virus particles (bacteriophages) that physically transfer genetic DNA from one bacteria to another called tranduction. Looks like misquitos biting or UFO's landing. They splice open the plasmids (equiv to our DNA helix) with enzymes then add genetic material. Then there is conjugation where they transfer genetic material by direct contact and transformation whereby they pick up random genetic material (from mammals, palnts other bacteria) and see if it works. like garbage collectors. Between the 3 mechanisms describes the phenomenal rate of bacterial mutation and why Antibiotics can be easily outsmarted. Once a single bacterium mutates beyond the drug itconfers this protection to all others. As for the plasmid DNA... humans actually carry them in our mitochondria (energy cells) which means at some point in our evolution we incorporated them into our anatomy.