Obligate aerobes are organisms that require oxygen for cellular respiration. They depend on oxygen to generate ATP through aerobic metabolism.
Organisms that can switch between aerobic and anaerobic metabolism depending on the presence of oxygen.
Microaerophiles: Organisms that require low levels of oxygen for growth but are inhibited by atmospheric concentrations.
Anaerobes: Organisms that do not require oxygen for growth and may even be killed by its presence.