Anaerobic organism

Information about Anaerobic organism

Enlarge picture
Aerobic and anaerobic bacteria can be identified by growing 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.
  • 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.

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.

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.

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 or botulinum toxins) that are highly dangerous to higher organisms, including humans.

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

Plantae
  • Chromalveolata
  • Heterokontophyta
  • Haptophyta
  • Cryptophyta
  • Alveolata

  • ..... Click the link for more information.
    • 2, −1
    (neutral oxide)
    Electronegativity 3.44 (Pauling scale)
    Ionization energies
    (more) 1st: 1313.9 kJmol−1
    2nd: 3388.3 kJmol−1
    3rd: 5300.5 kJmol−1

    Atomic radius 60 pm
    Atomic radius (calc.
    ..... Click the link for more information.
    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. In contrast, obligate anaerobes die in presence of oxygen.
    ..... Click the link for more information.
    An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process.
    ..... Click the link for more information.
    Microaerophilic organisms are a specific type of organism that requires oxygen to survive, but requires environments containing lower levels of oxygen than are present in the atmosphere (~20% concentration).
    ..... Click the link for more information.
    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 (eg Bacteroides fragilis).
    ..... Click the link for more information.
    Fermentation is a process of energy production in a cell under anaerobic conditions (with no oxygen required). In common usage fermentation is a type of anaerobic respiration, however a more strict definition exists which defines fermentation as respiration under anaerobic
    ..... Click the link for more information.
    The factual accuracy of part of this article is disputed.
    The dispute is about Lactic acid fermentation.
    Please see the relevant discussion on the talk page .
    ..... Click the link for more information.
    Cellular respiration describes the metabolic reactions and processes that take place in a cell or across the cell membrane to obtain biochemical energy from fuel molecules and the release of the cells' waste products.
    ..... Click the link for more information.
    Glucose (Glc), a monosaccharide (or simple sugar), is an important carbohydrate in biology. The living cell uses it as a source of energy and metabolic intermediate.
    ..... Click the link for more information.
    Adenosine diphosphate, abbreviated ADP, is a nucleotide. It is an ester of pyrophosphoric acid with the nucleotide adenine. ADP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase adenine.
    ..... Click the link for more information.
    Lactic acid (IUPAC systematic name: 2-hydroxypropanoic acid), also known as milk acid, is a chemical compound that plays a role in several biochemical processes.
    ..... Click the link for more information.
    Adenosine 5'-triphosphate (ATP) is a multifunctional nucleotide that is most important as a "molecular currency" of intracellular energy transfer. In this role, ATP transports chemical energy within cells for metabolism.
    ..... Click the link for more information.
    The joule per mole (symbol: J·mol-1) is an SI derived unit of energy per amount of material. Energy is measured in joules, and the amount of material is measured in moles.
    ..... Click the link for more information.
    Archaea
    Woese, Kandler & Wheelis, 1990

    Phyla

    Crenarchaeota
    Euryarchaeota
    Korarchaeota
    Nanoarchaeota
    ARMAN
    The Archaea (
    ..... Click the link for more information.
    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.
    ..... Click the link for more information.
    Butyric acid, (from Greek βουτυρος = butter) IUPAC name n-Butanoic acid, or normal butyric acid, is a carboxylic acid with structural formula CH3CH2CH2-COOH.
    ..... Click the link for more information.
    2,3-Butanediol fermentation is anaerobic fermentation of glucose with 2,3-Butanediol as one of the end products. The overall stoichiometry of the reaction is 2 pyruvate + NADH --> 2CO2 + butanediol.
    ..... Click the link for more information.
    Stickland fermentation is the name for a chemical reaction that involves the coupled oxidation and reduction of amino acids to organic acids. The electron donor amino acid is oxidised to a volatile carboxylic acid one carbon atom shorter than the original amino acid.
    ..... Click the link for more information.
    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. The different bacterial species that are capable of acetogenesis are collectively termed acetogens.
    ..... Click the link for more information.
    Methanogenesis or biomethanation is the formation of methane by microbes known as methanogens. Organisms capable of producing methane have been identified only from the kingdom Archaea, a group phylogenetically distinct from both eukaryotes and bacteria, although many live
    ..... Click the link for more information.
    toxin (Greek: τοξικόν, toxikon, lit. (poison) for use on arrows) is a poisonous substance produced by living cells or organisms.
    ..... Click the link for more information.
    aerobic organism or aerobe is an organism that has an oxygen based metabolism. Aerobes, in a process known as cellular respiration, use oxygen to oxidize substrates (for example sugars and fats) in order to obtain energy.
    ..... Click the link for more information.
    Anaerobic digestion (AD) is the natural process of biological degradation of organic material in the absence of air. An anaerobic digester is a man-made system that harnesses this process to treat waste and produce biogas and anaerobic digestate, a soil-improving material.
    ..... Click the link for more information.
    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.
    ..... Click the link for more information.
    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. In contrast, obligate anaerobes die in presence of oxygen.
    ..... Click the link for more information.
    Fermentation is a process of energy production in a cell under anaerobic conditions (with no oxygen required). In common usage fermentation is a type of anaerobic respiration, however a more strict definition exists which defines fermentation as respiration under anaerobic
    ..... Click the link for more information.
    Waste management is the collection, transport, processing, recycling or disposal of waste materials, usually ones produced by human activity, in an effort to reduce their effect on human health or local aesthetics or amenity.
    ..... Click the link for more information.

    This article is copied from an article on Wikipedia.org - the free encyclopedia created and edited by online user community. The text was not checked or edited by anyone on our staff. Although the vast majority of the wikipedia encyclopedia articles provide accurate and timely information please do not assume the accuracy of any particular article. This article is distributed under the terms of GNU Free Documentation License.