Anaerobes

Aharon Oren, The Hebrew University of Jerusalem, Jerusalem, Israel

Published online: June 2011

DOI: 10.1002/9780470015902.a0020369.pub2

Abstract

A diverse world of microorganisms inhabits anaerobic environments on Earth, and these obtain their energy by fermentation or by anaerobic respiration, in which electron acceptors other than molecular oxygen drive the oxidation of organic compounds. We also know phototrophic and chemoautotrophic processes that function in the absence of oxygen. Collaboration of different groups of microorganisms can lead to degradation of complex organic matter also under anaerobic conditions, with carbon dioxide or a mixture of carbon dioxide and methane as the main products, depending on the availability of electron acceptors other than molecular oxygen, such as nitrate or sulfate. The different groups of anaerobes are essential for the functioning of the biogeochemical cycles of carbon, nitrogen, sulfur and other elements, and also play important roles in the production of fermented food products, treatment of organic wastes and other biotechnological processes.

Key Concepts:

  • Life developed on planet Earth in the absence of molecular oxygen (O2).

  • The anaerobic way of life is widespread in the prokaryotic world – in Bacteria as well as Archaea.

  • Permanently anaerobic environments include marine and freshwater lake bottom sediments, digestive systems, the deep subsurface and others.

  • Some protozoa can live anaerobically.

  • Recently a community of multicellular meiozoa that lives in permanently anoxic conditions was discovered in L'Atalante basin, 3.5 km below the surface of the Mediterranean Sea.

  • In the absence of molecular oxygen, many prokaryotes can use alternative electron acceptors, such as nitrate, sulfate, Fe(III) and others, for respiration (‘anaerobic respiration’).

  • When no suitable electron acceptor is available, energy can be gained by fermentation processes, in which ATP is gained by substrate‐level phosphorylation.

  • Complete anaerobic breakdown of organic matter is a cooperative process in which fermentative microorganisms, bacteria performing anaerobic respiration and methanogenic Archaea cooperate.

  • Hydrogen and acetate are key intermediates in many anaerobic degradation processes.

Keywords: oxygen; anaerobic; denitrification; sulfate reduction; fermentation; methanogenesis

Figure 1.

Comparison of two modes of anaerobic respiration – denitrification and dissimilatory sulfate reduction – and aerobic respiration. In each case reduced organic substrates are oxidised, and the electrons released are transferred through membrane‐bound electron carriers with conservation of energy in the form of ATP. Molecular oxygen, the terminal electron acceptor in aerobic respiration, is replaced by electron acceptors such as nitrate and sulfate in anaerobic respiration processes. Note that most bacteria that perform denitrification are capable of aerobic respiration as well.

Figure 2.

The principle of fermentation, as exemplified by the homolactic fermentation of Lactobacillus and Streptococcus species and by the alcohol fermentation of yeasts. Organic substrates are degraded to simpler compounds without involvement of an external electron acceptor. Part of the energy released is conserved in the form of ATP.

Figure 3.

Different scenarios of degradation of complex organic material: in the presence of external electron acceptors such as sulfate and possibly nitrate (left panel), complete breakdown to CO2+CH4 in the absence of such electron acceptors (middle panel), and partial breakdown occurs in the rumen of ruminant animals, with production of the organic acids acetate, propionate and butyrate which are used by the animal, in addition to minor amounts of carbon dioxide and CH4. In all cases, the degradation is effected by combination of fermentative processes and other types of metabolism, including anaerobic respiration, methanogenesis and syntrophy. The schemes show the principal steps in the degradation processes only.

Figure 4.

An example of syntrophic growth in which two bacteria cooperate to degrade a substrate. The conversion of ethanol into acetate and molecular hydrogen by the ‘S‐organism’ is energetically favourable only when methanogenic Archaea in close physical contact maintain the concentration of hydrogen at very low levels by interspecies hydrogen transfer.

close

References

Boetius A, Ravenschlag K, Schubert CJ et al. (2000) A marine microbial consortium apparently mediating anaerobic oxidation of methane. Nature 407: 623–626.

Chivian D, Brodie EL, Alm EJ et al. (2008) Environmental genomics reveals a single‐species ecosystem deep within Earth. Science 322: 275–278.

Dalsgaard T, Canfield DE, Petersen J et al. (2003) N2 production by the anammox reaction in the anoxic water column of Golfo Dulce, Costa Rica. Nature 422: 606–608.

Danovaro R, Dell'Anno A, Pusceddu A et al. (2010) The first metazoan living in permanently anoxic conditions. BMC Biology 8: 30.

Ettwig KF, Butler MK, Le Paslier D et al. (2010) Nitrite‐driven anaerobic methane oxidation by oxygenic bacteria. Nature 464: 543–548.

Francis CA, Berman JM and Kuypers MMM (2007) New processes and players in the nitrogen cycle: the microbial ecology of anaerobic and archaeal ammonia oxidation. The ISME Journal 1: 19–27.

Gibson J and Harwood CS (2002) Metabolic diversity in aromatic compound utilization by anaerobic microbes. Annual Reviews of Microbiology 56: 345–369.

Hallam SJ, Putnam N, Preston CM et al. (2004) Reverse methanogenesis: testing the hypothesis with environmental genomics. Science 305: 1457–1462.

Hansen TA (1994) Metabolism of sulfate‐reducing prokaryotes. Antonie van Leeuwenhoek 66: 165–184.

Harwood CS, Burchhardt G, Herrmann H et al. (1999) Anaerobic metabolism of aromatic compounds via the benzoyl‐CoA pathway. FEMS Microbiology Reviews 22: 439–458.

Hungate RE (1966) The Rumen and its Microbes. New York: Academic Press.

Kuypers MMM, Sliekers AO, Lavik G et al. (2003) Anaerobic ammonium oxidation by anammox bacteria in the Black Sea. Nature 422: 608–611.

Levin LA (2010) Anaerobic metazoans: no longer an oxymoron. BMC Biology 8: 31.

Lloyd JR (2003) Microbial reduction of metals and radionuclides. FEMS Microbiology Reviews 27: 411–425.

Lovley D (2006) Dissimilatory Fe(III)‐ and Mn(IV)‐reducing prokaryotes. In: Dworkin M, Falkow S, Rosenberg E et al. (eds) The Prokaryotes. A Handbook on the Biology of Bacteria: Ecophysiology and Biochemistry, vol. 2, pp. 635–658. New York: Springer.

Lovley DR (1993) Dissimilatory metal reduction. Annual Review of Microbiology 47: 263–290.

Lovley DR, Holmes DE and Nevin KP (2004) Dissimilatory Fe(III) and Mn(IV) reduction. Advances in Microbial Physiology 49: 219–286.

Moodie AD and Ingledew WJ (1990) Microbial anaerobic respiration. Advances in Microbial Physiology 31: 225–269.

Nealson KH and Saffarini DA (1994) Iron and manganese in anaerobic respiration: environmental significance, physiology, and regulation. Annual Review of Microbiology 48: 311–343.

Overmann J and Garcia‐Pichel F (2006) The phototrophic way of life. In: Dworkin M, Falkow S, Rosenberg E et al. (eds) The Prokaryotes. A Handbook on the Biology of Bacteria: Ecophysiology and Biochemistry, vol. 1, pp. 32–85. New York: Springer.

Payne WJ (1981) Denitrification. New York: Wiley‐Interscience.

Piña‐Ochoa E, Høgslund S, Geslin E et al. (2010) Widespread occurrence of nitrate storage and denitrification among Foraminifera and Gromiida. Proceedings of the National Academy of Sciences of the United States of America 107: 1148–1153.

Rabus R, Hansen TA and Widdel F (2006) Dissimilatory sulfate‐ and sulfite‐reducing prokaryotes. In: Dworkin M, Falkow S, Rosenberg E et al.(eds) The Prokaryotes. A Handbook on the Biology of Bacteria: Ecophysiology and Biochemistry, vol. 2, pp. 659–768. New York: Springer.

Raghoebarsing AA, Pol A, van de Pas‐Schoonen KT et al. (2006) A microbial consortium couples anaerobic methane oxidation to denitrification. Nature 440: 918–921.

Risgaard‐Petersen N, Langezaal AM, Ingvardsen S et al. (2006) Evidence for complete denitrifiation in a benthic foraminifer. Nature 443: 93–96.

Schink B (1997) Energetics of syntrophic cooperation in methanogenic degradation. Microbiology and Molecular Biology Reviews 61: 262–280.

Schink B and Stams AJM (2006) Syntrophism among prokaryotes. In: Dworkin M, Falkow S, Rosenberg E et al. (eds) The Prokaryotes. A Handbook on the Biology of Bacteria: Ecophysiology and Biochemistry, vol. 2, pp. 309–335. New York: Springer.

Shapleigh JP (2006) The denitrifying prokaryotes. In: Dworkin M, Falkow S, Rosenberg E et al. (eds) The Prokaryotes. A Handbook on the Biology of Bacteria: Ecophysiology and Biochemistry, pp. 769–792. New York: Springer.

Stams AJM (1994) Metabolic interactions between anaerobic bacteria in methanogenic environments. Antonie van Leeuwenhoek 66: 271–294.

Strous M and Jetten MSM (2004) Anaerobic oxidation of methane and ammonium. Annual Review of Microbiology 58: 99–117.

Strous M, Pelletier E, Mangenot S et al. (2006) Deciphering the evolution and metabolism of an anammox bacterium from a community genome. Nature 440: 790–794.

Thamdrup B (2000) Bacterial manganese and iron reduction in aquatic sediments. Advances in Microbial Ecology 16: 41–84.

Whitman WB, Bowen TL and Boone DR (2006) The methanogenic bacteria. In: Dworkin M, Falkow S, Rosenberg E et al. (eds) The Prokaryotes. A Handbook on the Biology of Bacteria: Ecophysiology and Biochemistry, vol. 3, pp. 165–207. New York: Springer.

Widdel F and Rabus R (2001) Anaerobic biodegradation of saturated and aromatic hydrocarbons. Current Opinion in Biotechnology 12: 259–276.

Wolin MJ (1979) The rumen fermentation: a model for microbial interactions in anaerobic ecosystems. Advances in Microbial Ecology 3: 49–77.

Zehnder AJB and Svensson BH (1986) Life without oxygen: what can and what cannot? Experientia 42: 1197–1205.

Zumft WG (1997) Cell biology and molecular basis of denitrification. Microbiology and Molecular Biology Reviews 61: 533–616.

Further Reading

Barton LL and Hamilton WA (2007) Sulphate‐Reducing Bacteria: Environmental and Engineered Systems. Cambridge: Cambridge University Press.

Blankenship RE, Madigan MT and Bauer CE (eds) (1995) Anoxygenic Photosynthetic Bacteria. Dordrecht: Kluwer Academic Publishers.

Broda E (1975) The Evolution of the Bioenergetic Processes. Oxford: Pergamon Press.

Gottschalk G (1986) Bacterial Metabolism. Berlin: Springer.

Lengeler JW, Drews G and Schlegel HG (1999) Biology of the Prokaryotes. Stuttgart: Thieme.

Madigan MT, Martinko JM, Dunlap PV et al. (2009) Brock Biology of Microorganisms, 12th edn. San Francisco: Pearson/Benjamin Cummings.

Postgate JR (1984) The Sulphate‐Reducing Bacteria. Cambridge: Cambridge University Press.

Schmitz R, Daniel R, Deppenmeier U et al. (2006) The anaerobic way of life. In: Dworkin M, Falkow S, Rosenberg E et al. (eds) The Prokaryotes. A Handbook on the Biology of Bacteria: Ecophysiology and Biochemistry, vol. 2, pp. 86–101. New York: Springer.

Thauer RK, Jungermann K and Decker K (1977) Energy conservation in chemotrophic anaerobic bacteria. Bacteriological Reviews 41: 100–180.

Zinder SH and Dworkin M (2006) Morphological and physiological diversity. In: Dworkin M, Falkow S, Rosenberg E et al. (eds) The Prokaryotes. A Handbook on the Biology of Bacteria: Ecophysiology and Biochemistry, vol. 1, pp. 185–220. New York: Springer.

Related Sub-Topics:

Origin of Life | Bacteria | Energetics and Catabolism | Microbial Evolution and Taxonomy | Environmental Microbiology | Diversity of Life | Biogeochemical Cycles | Microbial Respiration and Fermentation
Contact Editor close
Submit a note to the editor about this article by filling in the form below.

* Required Field

Article Title: Anaerobes
 
How to Cite close
Oren, Aharon(Jun 2011) Anaerobes. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0020369.pub2]