A Movable Defense: The virome and our genomes| The Scientist Magazine®

Researchers now recognize that genetic material, once simplified into neat organismal packages, is not limited to individuals or even species. Viruses that pack genetic material into stable infectious particles can incorporate some or all of their genes into their hosts’ genomes, allowing remnants of infection to remain even after the viruses themselves have moved on. On a smaller scale, naked genetic elements such as bacterial plasmids and transposons, or jumping genes, often shuttle around and between genomes. It seems that the entire history of life is an incessant game of tug-of-war between such mobile genetic elements (MGEs) and their cellular hosts.

MGEs pervade the biosphere. In all studied habitats, from the oceans to soil to the human intestine, the number of detectable virus particles, primarily bacteriophages, exceeds the number of cells at least tenfold, and maybe much more. Furthermore, MGEs and their remnants constitute large portions of many organisms’ genomes—as much as two-thirds of the human genome and up to 90 percent in plants such as corn.

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