Aerobic and anaerobic bacteria can be identified by growning them in liquid culture:
1: Obligate aerobic bacteria gather at the top of the test tube in order to absorb maximal amount of oxygen.
2: Obligate anaerobic bacteria gather at the bottom to avoid oxygen.
3: Facultative bacteria gather mostly at the top, since aerobic respiration is the most beneficial one; but as lack of oxygen does not hurt them, they can be found all along the test tube.
4: Microaerophiles gather at the upper part of the test tube but not at the top. They require oxygen but at a low concentration.
5: Aerotolerant bacteria are not affected at all by oxygen, and they are evenly spread along the test tube.

An anaerobic organism is any organism that does not require oxygen for growth. Image File history File links Size of this preview: 800 × 479 pixels Full resolution (865 × 518 pixel, file size: 17 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Aerobic organism Anaerobic organism ... Image File history File links Size of this preview: 800 × 479 pixels Full resolution (865 × 518 pixel, file size: 17 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Aerobic organism Anaerobic organism ... This article does not cite any references or sources. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ...

• Obligate anaerobes will die when exposed to atmospheric levels of oxygen.
• Facultative anaerobes can use oxygen when it is present.
• Aerotolerant organisms can survive in the presence of oxygen, but they are anaerobic because they do not use oxygen as a terminal electron acceptor.

Microaerophiles are organisms that may use oxygen, but only at low concentrations (low micromolar range); their growth is inhibited by normal oxygen concentrations (approximately 200 micromolar). Nanaerobes are organisms that cannot grow in the presence of micromolar concentrations of oxygen, but can grow with and benefit from nanomolar concentrations of oxygen. A facultative anaerobic organism is an organism, usually a bacterium, that makes ATP by aerobic respiration if oxygen is present but is also capable of switching to fermentation under anaerobic conditions. ... An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. ... Microaerophilic organisms are a specific type of organism that requires oxygen to survive, but requires or can tolerate environments containing lower levels of oxygen than are present in the atmosphere (~20% concentration). ... Nanaerobes are organisms that cannot grow in the presence of micromolar concentrations of oxygen, but can grow with and benefit from the presence of nanomolar concentrations of oxygen. ...

Obligate anaerobes may use fermentation or anaerobic respiration. In the presence of oxygen, facultative anaerobes use aerobic respiration; without oxygen some of them ferment, some use anaerobic respiration. Aerotolerant organisms are strictly fermentative. Microaerophiles carry out aerobic respiration, and some of them can also do anaerobic respiration. This article or section does not cite any references or sources. ... Anaerobic respiration refers to the oxidation of molecules in the absence of oxygen to produce energy, in opposition to Aerobic respiration which does use oxygen. ... This article or section should be merged with aerobic metabolism. ...

There are many chemical equations for 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. Glucose (Glc), a monosaccharide (or simple sugar), is the most important carbohydrate in biology. ... Adenosine diphosphate, abbreviated ADP, is a nucleotide. ... For the production of milk by mammals, see Lactation. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... Kilojoule per mole are an SI derived unit of energy per amount of material, where energy is measured in units of 1000 joules, and the amount of material is measured in mole units. ...

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. Phyla Crenarchaeota Euryarchaeota Korarchaeota Nanoarchaeota Archaea are a major division of microorganisms. ... Propionic acid (systematically named propanoic acid) is a naturally occurring carboxylic acid with chemical formula CH3CH2COOH. In the pure state, it is a colorless, corrosive liquid with a pungent odor. ... Butyric acid, (from Greek βουτυρος = butter) IUPAC name n-Butanoic acid, or normal butyric acid, is a carboxylic acid with structural formula CH3CH2CH2-COOH. It is notably found in rancid butter, parmesan cheese, and vomit, and has an unpleasant odor and acrid taste, with a sweetish aftertaste (similar to ether). ... 2,3-Butanediol fermentation is anaerobic fermentation of glucose with 2,3-Butanediol as one of the end products. ... This article needs to be cleaned up to conform to a higher standard of quality. ... Acetogenesis is a process through which acetate is produced by anaerobic bacteria from a variety of energy (for example, hydrogen) and carbon (for example, carbon dioxide) sources. ... Methanogenesis is the formation of methane by microbes. ...

Some anaerobic bacteria produce toxins (e.g., tetanus or botulinum toxins) that are highly dangerous to higher organisms, including humans. This article or section does not cite any references or sources. ...

Obligate (strict) anaerobes die in presence of oxygen due to the absence of the enzymes superoxide dismutase and catalase which would convert the lethal superoxide formed in their cells due to the presence of oxygen.

See also

• Aerobic organism
• Anaerobic digestion
• Biogas
• Facultative anaerobic organism
• Fermentation (biochemistry)

• Waste management

Aerobic and anaerobic bacteria can be identified by growning them in liquid culture: 1: Obligate aerobic bacteria gather at the top of the test tube in order to absorb maximal amount of oxygen. ... Anaerobic digestion is the breakdown of organic matter by bacteria in the absence of oxygen. ... Biogas-bus in Bern, Switzerland Biogas typically refers to a (biofuel) gas produced by the anaerobic digestion or fermentation of organic matter including manure, sewage sludge, municipal solid waste, biodegradable waste or any other biodegradable feedstock, under anaerobic conditions. ... A facultative anaerobic organism is an organism, usually a bacterium, that makes ATP by aerobic respiration if oxygen is present but is also capable of switching to fermentation under anaerobic conditions. ... This article or section does not cite any references or sources. ... Wikimedia Commons has media related to: Waste For the company, see Waste Management, Inc. ...