Aerotolerant anaerobes use fermentation to produce ATP. They do not utilize oxygen, but they can protect themselves from reactive oxygen molecules. In contrast, obligate anaerobes can be harmed by reactive oxygen molecules.
There are three categories of anaerobes. Obligate anaerobes are damaged by the presence of oxygen. Aerotolerant organisms cannot use oxygen for growth but tolerate its presence. Obligate Aerobes require oxygen to grow. Facultative anaerobes can grow without oxygen but use oxygen if it is present.
- WI, Kenneth Todar, Madison. "Nutrition and Growth of Bacteria".