Anaerobic respiration

Source: Wikipedia, the free encyclopedia.
Not to be confused with Fermentation.

Anaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2). Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain.[1]

In

fumarate (C
4H
2O2−
4), sulfate (SO2−
4), or elemental sulfur (S). These terminal electron acceptors have smaller reduction potentials
than O2. Less energy per oxidized molecule is released. Therefore, anaerobic respiration is less efficient than aerobic.

As compared with fermentation

Anaerobic cellular respiration and

protons down the gradient (across the membrane) through the proton channel of ATP synthase. The resulting current drives ATP synthesis from ADP and inorganic phosphate.[citation needed
]

pyruvate to lactic acid at a later stage in the pathway. In yeast, acetaldehyde is reduced to ethanol to regenerate NAD+.[citation needed
]

There are two important anaerobic microbial methane formation pathways, through carbon dioxide / bicarbonate (HCO−
3) reduction (respiration) or acetate fermentation.[2]

Ecological importance

Anaerobic respiration is a critical component of the global

global warming. Anaerobic respiration occurs in many environments, including freshwater and marine sediments, soil, subsurface aquifers, deep subsurface environments, and biofilms. Even environments that contain oxygen, such as soil, have micro-environments that lack oxygen due to the slow diffusion characteristics of oxygen gas.[citation needed
]

An example of the ecological importance of anaerobic respiration is the use of nitrate as a

sulfidic metal ores.[6]

Economic relevance

Anaerobic Denitrification (ETC System)

The model above shows the process of anaerobic respiration through denitrification, which uses nitrogen (in the form of nitrate, NO−
3) as the electron acceptor. NO−
3 goes through respiratory dehydrogenase and reduces through each step from the ubiquinose through the bc1 complex through the ATP synthase protein as well. Each reductase removes oxygen step by step so that the final product of anaerobic respiration is N2.

1. Cytoplasm
2. Periplasm Compare to the aerobic electron transport chain.

Dissimilatory denitrification is widely used in the removal of nitrate and nitrite from municipal wastewater. An excess of nitrate can lead to eutrophication of waterways into which treated water is released. Elevated nitrite levels in drinking water can lead to problems due to its toxicity. Denitrification converts both compounds into harmless nitrogen gas.[7]

Specific types of anaerobic respiration are also critical in

chlorinated chemical pollutants, such as vinyl chloride and carbon tetrachloride, also occurs through anaerobic respiration.[citation needed][8]

Anaerobic respiration is useful in generating electricity in microbial fuel cells, which employ bacteria that respire solid electron acceptors (such as oxidized iron) to transfer electrons from reduced compounds to an electrode. This process can simultaneously degrade organic carbon waste and generate electricity.[9]

Examples of electron acceptors in respiration

Type Lifestyle Electron acceptor Products Eo′ (V) Example organisms
Aerobic respiration
facultative anaerobes
 O2 H2O, CO2 +0.82
prokaryotes
Perchlorate respiration
Facultative anaerobes
 ClO−
4, ClO−
3 		H2O, O2, Cl− +0.797
prokaryotes[10]
Iodate respiration
Facultative anaerobes
 IO−
3 		H2O, H2O2, I− +0.72
prokaryotes[12]
Iron reduction
Facultative anaerobes and obligate anaerobes
 Fe(III) Fe(II) +0.75 Organisms within the order Desulfuromonadales (such as Geobacter, Geothermobacter, Geopsychrobacter, Pelobacter) and Shewanella species [13]
Manganese
Facultative anaerobes and obligate anaerobes
 Mn(IV) Mn(II) Desulfuromonadales and Shewanella species [13]
Cobalt reduction
Facultative anaerobes and obligate anaerobes
 Co(III) Co(II) Geobacter sulfurreducens
Uranium reduction
Facultative anaerobes and obligate anaerobes
 U(VI) U(IV) Geobacter metallireducens, Shewanella oneidensis[14]
Nitrate reduction (denitrification)
Facultative anaerobes
 Nitrate NO−
3 		(Ultimately) N2 +0.40 Paracoccus denitrificans, Escherichia coli
Fumarate respiration
Facultative anaerobes
Fumarate
Succinate
 +0.03 Escherichia coli
Sulfate respiration
 Obligate anaerobes Sulfate SO2−
4 		Sulfide HS− −0.22 Many
Deltaproteobacteria species in the orders Desulfobacterales, Desulfovibrionales, and Syntrophobacterales
Methanogenesis (carbon dioxide reduction)
Methanogens
 Carbon dioxide CO2 Methane CH4 −0.25 Methanosarcina barkeri
Sulfur respiration (sulfur reduction)
Facultative anaerobes and obligate anaerobes
 Sulfur S0 Sulfide HS− −0.27 Desulfuromonadales
Acetogenesis (carbon dioxide reduction) Obligate anaerobes Carbon dioxide CO2 Acetate −0.30 Acetobacterium woodii
Dehalorespiration
Facultative anaerobes and obligate anaerobes
 Halogenated organic compounds R–X Halide ions and dehalogenated compound X− + R–H +0.25 – +0.60[15] Dehalococcoides and Dehalobacter species

See also

Further reading

  • Gregory, Kelvin B.; Bond, Daniel R.; Lovley, Derek R. (June 2004). "Graphite electrodes as electron donors for anaerobic respiration". Environmental Microbiology. 6 (6): 596–604.
    PMID 15142248
    .

References

  1. ISBN 9780393934472
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  2. doi:10.5194/bg-14-2283-2017
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  3. PMID 22842521
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  5. S2CID 29740189
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  6. PMID 22403575
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  7. PMID 27053446
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  8. S2CID 239140980
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  9. ISSN 2053-1419
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  10. PMID 21856823
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  11. S2CID 235722250
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  12. bioRxiv 10.1101/2020.12.28.424624
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  13. ^
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  14. PMID 16704344
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  15. S2CID 85965965
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