Oxygen Requirements for Pathogenic Bacteria

https://microbeonline.com/oxygen-requirements-for-pathogenic-bacteria/

Why oxygen is toxic to some bacteria and how bacteria detoxify toxic oxygen metabolites?

Several studies indicate that aerobes can survive in the presence of oxygen only by virtue of an elaborate system of defenses. Without these defenses key enzyme systems in the organisms fail to function and the organisms die.

Obligate anaerobes, which live only in the absence of oxygen, do not possess the defenses that make aerobic life possible and therefore can not survive in air.

The tolerance to oxygen is related to the ability of the bacterium to detoxify superoxide and hydrogen peroxide, produced as a byproduct of aerobic respiration.

The assimilation of glucose in aerobic condition results in the terminal generation of free radical superoxide (O2–). The superoxide is reduced by the enzyme superoxide dismutase to oxygen gas and hydrogen peroxide (H2O2).

Subsequently, the toxic hydrogen peroxide generated in this reaction is converted to water and oxygen by the enzyme catalase, which is found in aerobic and facultative bacteria, or by various peroxidases which are found in several aerotolerant anaerobes.