What is the difference between a facultative anaerobic organism and an aerotolerant organism?

Answer

Anaerobic means ‘occurring or being able to live without air’, where with ‘air’ oxygen is meant. Anaerobic organisms do not use oxygen to generate energy and can even be killed by oxygen. Using Anaerobic Organisms fermentation or anaerobic dissimilation.

There are different degrees:

• Obligate anaerobic organisms cannot survive in the presence of oxygen, or in other words oxygen is toxic for these bacteria (eg. Clostridium, Bifidobacterium).
• Optional (an)aerobic organisms can survive in the presence of oxygen aerobic dissimilate, but also survive through oxygen-independent processes (eg. Enterobacteriaceae, Staphylococcus, vibrio).
• Microaerophilic organisms do need oxygen, but thrive best at low oxygen tension.
• Aerotolerant Organisms are in principle anaerobic, but tolerate the presence of oxygen (e.g. lactic acid bacteria).

Ordinary yeast is optionally anaerobic. Many putrefactive bacteria are anaerobic. Some anaerobic organisms are very useful, for example the butyric acid bacteria.

Anaerobic Archaea be used in activated sludge sewage treatment plantswithout oxygen and with water, Archaea convert dissolved organic substances into carbon dioxide and methane (biogas).