Aerobic organism: Difference between revisions

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	] is an example of a facultative anaerobe, which can develop in the presence of oxygen but does not require it. Individual ] are also facultative anaerobes: they switch to ] ] if oxygen is not available. However, for the whole organism this cannot be sustained for long, and humans are therefore obligate aerobes.		] is an example of a facultative anaerobe, which can develop in the presence of oxygen but does not require it. Individual ] are also facultative anaerobes: they switch to ] ] if oxygen is not available. However, for the whole organism this cannot be sustained for long, and humans are therefore obligate aerobes.
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Revision as of 13:51, 21 February 2013

Aerobic and anaerobic bacteria can be identified by growing them in a 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 aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment. Facultative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.

Types

Obligate aerobes require oxygen for aerobic cellular respiration. In a process known as cellular respiration, these organisms use oxygen to oxidize substrates (for example sugars and fats) in order to obtain energy.

Facultative anaerobes can use oxygen, but also have anaerobic methods of energy production.

Microaerophiles are organisms that may use oxygen, but only at low concentrations.

Aerotolerant organisms can survive in the presence of oxygen, but they are anaerobic because they do not use it as a terminal electron acceptor.

Glucose

A good example would be the oxidation of glucose (a monosaccharide) in aerobic respiration.

C₆H₁₂O₆ + 6 O₂ + 38 ADP + 38 phosphate → 6 CO₂ + 6 H₂O + 38 ATP

Oxygen is used during the oxidation of glucose and water is produced.

This equation is a summary of what actually happens in three series of biochemical reactions: glycolysis, the Krebs cycle, and oxidative phosphorylation.

Diversity

Yeast is an example of a facultative anaerobe, which can develop in the presence of oxygen but does not require it. Individual human cells are also facultative anaerobes: they switch to lactic acid fermentation if oxygen is not available. However, for the whole organism this cannot be sustained for long, and humans are therefore obligate aerobes.

References

"aerobe" at Dorland's Medical Dictionary

Oxygen preference	Aerobic Obligate Facultative Anaerobic Facultative Obligate Microaerophile Nanaerobe Aerotolerant
Other	Extremophile Human microbiome Gut Lung Mouth Skin Vaginal (in pregnancy) Placental Uterine Salivary Microbial metabolism Nitrogen fixation Microbial ecology Primary nutritional groups Substrate preference Lipophilic Saccharophilic

Shape

Structure

Cell envelope	Cell membrane Cell wall: Peptidoglycan NAM NAG DAP Gram-positive bacteria only: Teichoic acid Lipoteichoic acid Endospore Gram-negative bacteria only: Bacterial outer membrane Porin Lipopolysaccharide Periplasmic space Mycobacteria only: Arabinogalactan Mycolic acid
Outside envelope	Bacterial capsule Slime layer S-layer Glycocalyx Pilus Fimbria Non-motile bacteria
Composite	Biofilm

Taxonomy
and evolution

Categories:

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