EXCERPT

Scientists have found some toxic DNA lurking inside a virus that infects bacteria. In addition to its own genes, the virus holds a gene for black widow spider venom and DNA from other animals, the researchers found. The findings suggest that either the virus snagged this foreign genetic material or that these other animals have stolen DNA from the virus, the researchers said.

Future research could find that such swapping across domains of life, from the most complex to the most ancient, is more common than previously thought, scientists say.