" Fresh in modern memory, for hamburger eaters anyway: Toxin gene transfer to E. coli bacteria in cattle,” Turner began. “Modern factory farming and slaughterhouse technique puts severe stress on the cattle, who send hormonal signals to their multiple tummies, their rumen. E. coli react to these signals by taking up phages—viruses for bacteria—that carry genes from another common gut bacteria, Shigella. Those genes just happen to code for Shiga toxin. The exchange does not hurt the cow, fascinating, no? But when a predator kills a cow-like critter in nature, and bites into the gut—which most do, eating half-digested grass and such, wild salad it’s called—it swallows a load of E. coli packed with Shiga toxin. That can make the predators—and us—very sick. Sick or dead predators reduce the stress on cows. It’s a clever relief valve. Now we sterilize our beef with radiation. All the beef. "
― Greg Bear , Darwin's Children (Darwin's Radio #2)