Examples of organisms that respires both aerobically and anaerobically.
An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present. [ There are three types:
obligate anaerobes, which cannot use oxygen for growth and are even harmed by it
aerotolerant organisms, which cannot use oxygen for growth, but tolerate the presence of it
facultative anaerobes, which can
grow without oxygen but can utilize oxygen if it is present
2 Culturing anaerobes
4 See also
Obligate anaerobes may use fermentation or anaerobic respiration.
Aerotolerant organisms are strictly fermentative.
In the presence of oxygen, facultative anaerobes use aerobic respiration; without oxygen some of them ferment, some use anaerobic respiration.
There are many anaerobic fermentative reactions.
Fermentative anaerobic organisms mostly use the lactic acid fermentation pathway:
C6H12O6 + 2 ADP + 2 phosphate ? 2 lactic acid + 2 ATP
The energy released in this equation is approximately 150 kJ per mol, which is conserved in regenerating two ATP from ADP per glucose. This is only 5% of the energy per sugar molecule that the typical aerobic reaction generates.
Plants and fungi (e.g., yeasts) generally use alcohol (ethanol) fermentation when oxygen becomes limiting:
C6H12O6 + 2 ADP + 2 phosphate ? 2 C2H5OH + 2 CO2 + 2 ATP
The energy released is about 180 kJ per mol, which is conserved in regenerating two ATP from ADP per glucose.
Anaerobic bacteria and archaea use these and many other fermentative pathways, e.g., propionic acid fermentation, butyric acid fermentation, solvent fermentation, mixed acid fermentation, butanediol fermentation, Stickland fermentation, acetogenesis or methanogenesis.
Some anaerobic bacteria produce toxins (e.g., tetanus)
Since normal microbial culturing occurs in atmospheric air which is an aerobic environment, the culturing of anaerobes poses a problem, and a number of techniques are employed by microbiologists when culturing anaerobic organisms. ]
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