Biologists often conceptualize species as characterized by possession of a protected gene pool. That is, that genetic traits, or genes, can be passed around between members of a kind, but that genes can't be passed to other species nor received from other species. We've learned, to our sorrow, that this isn't always the case. Bacteria manage to pass evolved resistance to an antibiotic to other bacteria, eventually rendering an antibiotic useless.
On a different level, evidence is accumulating that such so-called "lateral transference" was common among early life forms. It appears that some genes managed to move between lines even after they split apart evolutionarily. The result? We may never make sense of the earliest evolutionary history of life.
The distant ancestors of our desert organisms, and of ourselves, seem
to have incorporated genetic material of bacteria in yet another way—by making them
part of ourselves. Mitochondria, parts of cells that process energy, have their own
genetic matter--remnants from when they were free-living bacteria that took up life
inside the cell, eventually becoming one with it.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Pennisi, E. 2003. Passages found through labyrinth of bacterial evolution. Science, 301:745-746.