Poisoned by oxygen
Most life has cells that use oxygen and enjoy the efficient release of energy via aerobic respiration. But where oxygen levels fall organisms need to respire without it via a process called anaerobic respiration. Microbes such as Bifidobacterium are part of the natural community of anaerobic organisms. Bifidobacteria species are probiotics ("good" bacteria) that live in the intestines. Bifidobacteria can help break down food, absorb nutrients, and fight off "bad" organisms that might cause diseases.
