Suffocation by waste

We recall the earlier example of a single bacterium, which divides so frequently that it eventually outweighs the planet earth. However, in reality we do not see gigantic masses of bacteria on the earth – in fact, bacterial colonies usually do not even grow to the size of a penny. Laboratory bacteria placed in a dish filled with nutrients will indeed grow exponentially, but eventually die because they produce too much waste and exhaust the food supply. These bacterial colonies essentially suffocate in their own waste products. ((Michio Kaku, Hyperspace: a Scientific Odyssey through Parallel Universes, Time Warps, and the Tenth Dimension, p.290))