The Metabolism of Anammox


Anaerobic ammonium‐oxidizing (anammox) bacteria derive their energy for growth from the conversion of ammonium and nitrite into dinitrogen gas. The bacteria are the latest addition to the biogeochemical nitrogen cycle. The slowly growing micro‐organisms that belong to the Planctomycetes are characterized by a compartmentalized cell architecture featuring a central cell organelle, the ‘anammoxosome’. Membrane systems surrounding the different cellular compartments are composed of unique ‘ladderane’ lipid molecules. Although the metabolism has not been completely resolved, nitrogen formation seems to involve the intermediary formation of hydrazine, a most reactive and toxic compound. Anammox bacteria have been detected in many oxygen‐limited freshwater and marine ecosystems investigated. In the marine environment, over 50% of the nitrogen gas released is made by anammox bacteria. Application of the anammox process offers an attractive alternative to current wastewater treatment systems for the removal of fixed nitrogen.

Key concepts

  • Ammonium is converted under anaerobic conditions into dinitrogen gas by a newly discovered and specialized group of micro‐organisms, the anammox bacteria.

  • Anammox bacteria are chemolithoautotrophic organisms that gain their energy for growth from the conversion of the inorganic substrates ammonium and nitrite. Cell carbon is derived from carbon dioxide.

  • Anammox bacteria are characterised by a unique cell plan featuring a central cell organelle, the anammoxosome.

  • The lipids from anammox bacteria are composed of highly unusual ‘ladderane’ molecules.

  • The conversion of ammonium and nitrite into dinitrogen gas proceeds through the intermediary formation of the toxic and highly reactive hydrazine.

  • Anammox bacteria synthesize adenosine triphosphate (ATP) by an electrochemical proton gradient most likely established across the anammoxosome membrane.

  • In nature approximately 50% of the dinitrogen gas released into the atmosphere is made by anammox bacteria.

  • Anammox bacteria offer an economically attractive and environmentally friendly alternative to current wastewater treatment processes for the removal of fixed nitrogen.

Keywords: anammox; anammoxosome; ladderane lipids; hydrazine

Figure 1.

The central steps in the biogeochemical nitrogen cycle. (1) Nitrogen fixation, (2) aerobic ammonium oxidation, (3) nitrite oxidation, (4) nitrate reduction, (5) denitrification and (6) nitrite reduction to ammonium.

Figure 2.

Growth of anammox bacteria in a sequencing batch reactor. The figure shows the experimental set‐up of a reactor containing the red anammox bacteria (left) and fluorescence in situ hybridization (FISH) analysis of the bacterial population present in the reactor (right). For FISH analysis, anammox bacteria were specifically labelled with a red fluorescent probe; blue fluorescent micro‐organisms represent non‐anammox species visualized by DAPI staining.

Figure 3.

Transmission electron microscopy of Candidatus ‘Anammoxoglobus propionicus’ showing the anammoxosome (A) containing tubule‐like structures, riboplasm (R) containing the nucloid (N) opposed to the anammoxosome membrane, paryphoplasm (P) separated from the riboplasm by an (ICM) and the (CM). Scale bar, 200 nm. Adapted from Kartal et al. with permission from Elsevier.

Figure 4.

General structure of ladderane lipids from anammox bacteria.

Figure 5.

Hypothetical metabolism of anammox bacteria. (a) Anammox central catabolism; (b) central catabolism in connection nitrite oxidation to generate low‐redox‐potential electrons for cell carbon fixation. Abbreviations: Nir, nitrite reductase; HH, hydrazine hydrolase; HZO, hydrazine dehydrogenase; Nar, nitrate reductase; Q(H2), (reduced) ubiquinone; atp, F1F0 ATP synthase; fdh, formate dehydrogenase; nuo, NADH:ubiquinone oxidoreductase; RET, reversed electron transport. Symbols: red diamonds, cytochromes; yellow diamond, ferredoxin; solid arrows, reductions; dashed arrows, oxidations. Please note that the localization of the enzymic reactions and the direction of proton translocation are arbitrarily chosen, at which ΔΨ+ and ΔΨ are thought to represent the anammoxosome and riboplasmic compartments, respectively.



Arrigo KR (2005) Marine microorganisms and global nutrient cycles. Nature 437: 349–355.

Broda E (1977) Two kinds of lithotrophs missing in nature. Zeitschrift für Allgemeine Mikrobiologie 17: 491–493.

Fuerst JA (2005) Intracellular compartmentation in planctomycetes. Annual Review of Microbiology 59: 299–328.

Hamersley MR, Lavik G, Woebken D et al. (2007) Anaerobic ammonium oxidation in the Peruvian oxygen minimum zone. Limnologica Oceanografica 52: 923–933.

Jetten MSM, Horn SJ and van Loosdrecht MCM (1997) Towards a more sustainable municipal wastewater treatment system. Water Science and Technology 35: 171–180.

Jetten MSM, Schmid M, Schmidt I et al. (2002) Improved nitrogen removal by application of new nitrogen‐cycle bacteria. Reviews in Environmental Science and Biotechnology 1: 51–63.

Jetten MSM, Wagner M, Fuerst J et al. (2001) Microbiology and application of the anaerobic ammonium oxidation (‘anammox process’). Current Opinion in Biotechnology 12: 283–288.

Kartal B, Kuypers MMM, Lavik G et al. (2007a) Anammox bacteria disguised as denitrifiers: nitrate reduction to dinitrogen gas via nitrite and ammonium. Environmental Microbiology 9: 635–642.

Kartal B, Rattray J, van Niftrik L et al. (2007b) Candidatus ‘Anammoxoglobus propionicus’ gen. nov., sp. nov., a new propionate oxidizing species of anaerobic ammonium oxidizing bacteria. Systematic and Applied Microbiology 30: 39–49.

Kartal B, van Niftrik L, Rattray J et al. (2008) Candidatus ‘Brocadia fulgida’: an autofluorescent anaerobic ammonium oxidizing bacterium. FEMS Microbiology Ecology 63: 46–55.

Kindaichi T, Tsushima I, Ogasawara Y et al. (2007) In situ activity and spatial organization of anaerobic ammonium‐oxidizing (anammox) bacteria in biofilms. Applied and Environmental Microbiology 73: 4931–4939.

Kuypers MMM, Lavik G, Woebken D et al. (2005) Massive nitrogen loss from the Benguela upwelling system through anaerobic ammonium oxidation. Proceedings of the National Academy Sciences of the USA 102: 6478–6483.

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

Lam P, Jensen MM, Lavik G et al. (2007) Linking crenarchaeal and bacterial nitrification to anammox in the Black Sea. Proceedings of the National Academy Sciences of the USA 104: 7104–7109.

Lindsay MR, Webb RI, Strous M et al. (2001) Cell compartmentalisation in planctomycetes: novel types of structural organisation for the bacterial cell. Archives of Microbiology 175: 413–429.

Mulder A, Van de Graaf AA, Robertson LA and Kuenen JG (1995) Anaerobic ammonium oxidation discovered in a denitrifying fluidized‐bed reactor. FEMS Microbiology Ecology 16: 177–183.

Nielsen M, Bollmann A, Sliekers O et al. (2005) Kinetics, diffusional limitation and microscale distribution of chemistry and organisms in a CANON reactor. FEMS Microbiology Ecology 51: 247–256.

Richards FA (1965) Anoxic basins and fjords. In: Ripley JP and Skirrow G (eds) Chemical Oceanography. London: Academic Press.

Schalk J, de Vries S, Kuenen JG and Jetten MSM (2000) Involvement of a novel hydroxylamine oxidoreductase in anaerobic ammonium oxidation. Biochemistry 39: 5405–5412.

Shimamura M, Nishiyama T, Shigetomo H et al. (2007) Isolation of a multiheme protein from an anaerobic ammonium‐oxidizing enrichment culture with features of a hydrazine‐oxidizing enzyme. Applied and Environmental Microbiology 73: 1065–1072.

Shimamura M, Nishiyama T, Shinya K et al. (2008) Another multiheme protein, hydroxylamine oxidoreductase, abundantly produced in an anammox bacterium besides the hydrazine‐oxidizing enzyme. Journal of Bioscience and Bioengineering 105: 243–248.

Sinninghe Damsté JS, Strous M, Rijpstra WIC et al. (2002) Linearly concatenated cyclobutane lipids form a dense bacterial membrane. Nature 419: 708–712.

Sliekers AO, Derwort N, Gomez JLC et al. (2002) Completely autotrophic nitrogen removal over nitrite in one single reactor. Water Research 36: 2475–2482.

Strous M, Fuerst JA, Kramer EHM et al. (1999) Missing lithotroph identified as new planctomycete. Nature 400: 446–449.

Strous M, Heijnen JJ, Kuenen JG and Jetten MSM (1998) The sequencing batch reactor as a powerful tool for the study of slowly growing anaerobic ammonium‐oxidizing microorganisms. Applied Microbiology and Biotechnology 50: 589–596.

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.

Third KA, Sliekers AO, Kuenen JG and Jetten MSM (2001) The CANON system (completely autotrophic nitrogen‐removal over nitrite) under ammonium limitation: interaction and competition between three groups of bacteria. Systematic and Applied Microbiology 24: 588–596.

Van de Graaf AA, Mulder A, Debruijn P et al. (1995) Anaerobic oxidation of ammonium is a biologically mediated process. Applied and Environmental Microbiology 61: 1246–1251.

Van de Graaf AA, deBruijn P, Robertson LA, Jetten MSM and Kuenen JG (1997) Metabolic pathway of anaerobic ammonium oxidation on the basis of N‐15 studies in a fluidized bed reactor. Microbiology (UK) 143: 2415–2421.

Van der Star WRL, Abma WR, Blommers D et al. (2007) Startup of reactors for anoxic ammonium oxidation: experiences from the first full‐scale anammox reactor in Rotterdam. Water Research 41: 4149–4163.

Van Niftrik L, Geerts WJC, van Donselaar EG et al. (2008a) Linking ultrastructure and function in four genera of anaerobic ammonium‐oxidizing bacteria: cell plan, glycogen storage, and localization of cytochrome c proteins. Journal of Bacteriology 190: 708–717.

Van Niftrik L, Geerts WJC, van Donselaar EG et al. (2008b) Combined structural and chemical analysis of the anammoxosome: a membrane‐bounded intracytoplasmic compartment in anammox bacteria. Journal of Structural Biology 161: 401–410.

Further Reading

Dalsgaard T, Thamdrup B and Canfield DE (2005) Anaerobic ammonium oxidation (anammox) in the marine environment. Research in Microbiology 156: 457–464.

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

Jetten MS, Cirpus I, Kartal B et al. (2005) 1994–2004: 10 years of research on the anaerobic oxidation of ammonium. Biochemical Society Transactions 33(part 1): 119–123.

Jetten MS, Strous M, van de Pas‐Schoonen KT et al. (1998) The anaerobic oxidation of ammonium. FEMS Microbiology Reviews 22: 421–437.

Kuenen JG (2008) Anammox bacteria: from discovery to application. Nature Reviews in Microbiology 6: 320–326.

Op den Camp HJ, Kartal B, Guven D et al. (2006) Global impact and application of the anaerobic ammonium‐oxidizing (anammox) bacteria. Biochemical Society Transactions 34(part 1): 174–178.

Schmidt I, Sliekers O, Schmid M et al. (2003) New concepts of microbial treatment processes for the nitrogen removal in wastewater. FEMS Microbiology Reviews 27: 481–492.

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Kartal, Boran, Keltjens, Jan T, and Jetten, Mike SM(Dec 2008) The Metabolism of Anammox. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0021315]