If you’ve survived Shiga toxin and the after-effects of food poisoning, you may have been the innocent victim of a battle for survival between predator and prey. Bacteria that carry a virus (a bacteriophage) that packs the Shiga toxin gene (Stx) may depend on it for protection from bacterial predators like the ciliated protozoan Tetrahymena. A discovery by University at Buffalo biologists that may explain the evolution of a lethal toxin is providing new information that could lead to more effective treatments for humans who fall victim to it.