Predation is a central ecological and evolutionary force. Predation shapes communities of organisms and ecosystems, impacts upon the behavior of both prey and predator, and influences evolutionary trajectories. Most of our knowledge about predatory interactions results from animal studies. If prokaryotes emerged before the eukaryotic lineages, around 3.8 billion years ago, then the first predators may have been prokaryotic organisms preying upon other prokaryotes. Here, for the sake of simplicity, all prokaryotes will be referred to as “bacteria.”