The angler bacteria is a small animal, it is more of a virus instead of a bacterium. It has three segments, one for eating prey, one for protecting itself, and one to lure prey. The pattern lures in prey that think it is delicious food. One of it's biggest issues is the fact that it cannot move.
It lives in places with not much food, where cells have evolved to be able to look for it. This is essential because if organisms have not evolved to look for food, the angler bacteria cannot lure the prey in.