Obligate anaerobes are the organism that grows in the complete absence of oxygen. The presence of oxygen either kills or inhibits their growth. These organisms’ uses the process of fermentation for obtaining ATP molecule.
Whereas the facultative anaerobes are the organisms that live in the presence or absence of oxygen. That is they can switch between the aerobic and anaerobic type of metabolism. They grow by fermentation in the anaerobic condition and under aerobic condition they switch on to aerobic respiration.
