Aerobes

aerobic organisms, organisms having the aerobic type of respiration—that is, those capable of living and developing only in the presence of free oxygen. Almost all animals and plants—and many microorganisms—that for their life activities use energy liberated in oxidation reactions that occur with the absorption of free oxygen (that is, those having an oxidative type of metabolism) belong to the group of aerobes. Obligate aerobes and aerophiles obtain energy only from the oxidative reaction (for example, acetic-acid and nitrifying bacteria). Facultative aerobes (which are also conditional anaerobes) use the energy of fermentation, and therefore they can live with either large or negligible amounts of oxygen (for example, yeasts and denitrifying bacteria). Each species of aerobic bacteria has its own definite and characteristic maximal, minimal, and optimal oxygen concentrations.