Facultative anaerobic organism
A facultative anaerobe is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation or anaerobic respiration if oxygen is absent. An obligate aerobe, by contrast, cannot make ATP in the absence of oxygen, and obligate anaerobes die in the presence of oxygen.
Some examples of facultatively anaerobic bacteria are Staphylococcus spp., Escherichia coli, Shewanella oneidensis, and Listeria spp. Certain eukaryote phyla are also facultative anaerobes, including fungi such as yeasts and many aquatic invertebrates such as Nereid (worm) polychaetes. There are also circulating white blood cells that are classified as facultative anaerobes. These include neutrophils, monocytes and tissue macrophages.
The concentrations of oxygen and fermentable material in the environment influence the organism's use of aerobic respiration vs. fermentation to derive energy. In brewer's yeast, the Pasteur shift is the observed cessation of oxygen consumption when fermentable sugar is supplied. In a growing culture, the energy "economics" disfavors respiration due to the "overhead cost" of producing the apparatus, as long as sufficient fermentable substrate is available, even though the energy output per mole of fermented material is far less than from respiration's complete oxidation of the same substrate. However, the rate of production of ATP can be up to 100 times faster than that of oxidative phosphorylation. Therefore, tissues and organisms that require fast consumption of ATP preferentially use anaerobic glycolysis.
- Schöttler, U. (November 30, 1979). "On the Anaerobic Metabolism of Three Species of Nereis (Annelida)". Marine Ecology Progress Series 1: 249–54. ISSN 1616-1599. Retrieved February 14, 2010.
- Voet, Donald; Judith G. Voet, Charlotte W. Pratt (2002). Fundamentals of Biochemistry (Upgrade ed.). New York: Wiley. p. 400. ISBN 0-471-41759-9.
- Facultative Anaerobic Bacteria
- Obligate Anaerobic Bacteria
- Anaerobic Bacteria and Anaerobic Bacteria in the decomposition (stabilization) of organic matter.
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