Question

1. What is the molecular basis for the different relationships of these organisms to oxygen That is to say, why can’t an anaerobe grow with oxygen around? What do aerobic organisms have that allows them to survive in an oxygen atmosphere?

Answer 1

Obligate anaerobes cannot tolerate oxygen because they utilize metabolic schemes built around enzymes that react with oxidants. The reliance upon low-potential flavoproteins for anaerobic respiration probably causes substantial superoxide and hydrogen peroxide to be produced when anaerobes are exposed to air.

Most facultative and aerobic organism possesses a high concentration of an enzyme called superoxide dismutase. As anaerobes lack these enzymes that detoxify the toxic oxygen products, they cannot tolerate the toxic effects of oxygen and hence do not survive in presence of oxygen.