Aerotolerant anaerobes use

fermentation Fermentation is a type of anaerobic metabolism which harnesses the redox potential of the reactants to make adenosine triphosphate (ATP) and organic end products. Organic molecules, such as glucose or other sugars, are catabolized and reduce ...

to produce ATP. They do not use

oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

, but they can protect themselves from reactive oxygen molecules. In contrast,

obligate anaerobe Obligate anaerobes are microorganisms killed by normal Atmosphere of Earth, atmospheric concentrations of oxygen (20.95% O2). Oxygen tolerance varies between species, with some species capable of surviving in up to 8% oxygen, while others lose vi ...

s can be harmed by reactive oxygen molecules. There are three categories of anaerobes. Where obligate aerobes require oxygen to grow,

s are damaged by oxygen, aerotolerant organisms cannot use oxygen but tolerate its presence, and facultative anaerobes use oxygen if it is present but can grow without it. Most aerotolerant anaerobes have

superoxide dismutase Superoxide dismutase (SOD, ) is an enzyme that alternately catalyzes the dismutation (or partitioning) of the superoxide () anion radical into normal molecular oxygen (O2) and hydrogen peroxide (). Superoxide is produced as a by-product of oxy ...

and (non-catalase) peroxidase but do not have

catalase Catalase is a common enzyme found in nearly all living organisms exposed to oxygen (such as bacteria, plants, and animals) which catalyzes the decomposition of hydrogen peroxide to water and oxygen. It is a very important enzyme in protecting ...

. More specifically, they may use a NADH oxidase/ NADH peroxidase (NOX/NPR) system or a glutathione peroxidase system. An example of an aerotolerant anaerobe is '' Cutibacterium acnes''.

References

Microbiology {{microbiology-stub