nature always has other predator bacteria species that eat this amoeba. why can't we use them? there are must be numerous types of bacteria.

Our lives can't be crippled by a single species of amoeba. I am aware the amoeba always exist in lakes but other reasons must have trigger this problem. the rise in temperature can't be the only source for the increase of the amoeba. Nature has checks and balances for every species. What happened to the other bacteria that prey upon this amoeba species?