AskDefine | Define aerobe

Dictionary Definition

aerobe n : an organism especially a bacterium that requires air or free oxygen for life

User Contributed Dictionary

English

Noun

  1. Any organism (but especially a bacterium) that can tolerate the presence of oxygen, or that needs oxygen to survive

Extensive Definition

An 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.
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
The energy released in this equation is about 2880 kJ per mol, which is conserved in regenerating 38 ATP from 38 ADP per glucose. This is a factor of 19 times more energy per sugar molecule than the typical anaerobic reaction generates. Eukaryotic organisms (everything but bacteria) only get a net gain of 36 ATP regenerated from ADP in this process, due to an additional membrane that must be crossed by active transport.
Notice that 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.
Almost all animals, most fungi, and several bacteria are obligate aerobes. Most anaerobic organisms are bacteria. Being an obligate aerobe, although being advantageous from the energetical point of view, means also obligatory facing high levels of oxidative stress.
Yeast is an example of a facultative aerobe. Individual human cells are also facultative aerobes: 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.
Examples of Obligate Aerobic Bacteria: Nocardia (Gram-positive), Pseudomonas aeruginosa (Gram-negative), Mycobacterium tuberculosis (acid-fast), and Bacillus (Gram-positive).
aerobe in Bulgarian: Аероб
aerobe in Czech: Aerobní
aerobe in Danish: Aerob
aerobe in German: Aerobie
aerobe in Spanish: Organismo aeróbico
aerobe in Basque: Aerobio
aerobe in French: Aérobie
aerobe in Galician: Organismo aeróbico
aerobe in Indonesian: Organisme aerobik
aerobe in Italian: Aerobiosi
aerobe in Hebrew: אווירני
aerobe in Latvian: Aerobi organismi
aerobe in Macedonian: Аероб
aerobe in Dutch: Aeroob
aerobe in Japanese: 好気性生物
aerobe in Norwegian: Aerobe organismer
aerobe in Polish: Aeroby
aerobe in Portuguese: Aerobiose
aerobe in Russian: Аэробы
aerobe in Finnish: Aerobinen
aerobe in Swedish: Aerob
aerobe in Ukrainian: Аероби
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