A term in biochemistry: anammox for anaerobic ammonium oxidation

Anammox stands for anaerobic ammonium oxidation, a biochemical reaction that combines ammonium and nitrite (or nitrate) to form dinitrogen (N₂) gas and water [1-5]. This reaction is performed by aquatic anammox bacteria belonging to the planctomycete group. Using the bacterium Kuenenia stuttgartiensis, it has been shown recently that the reaction pathway involves nitric oxide and hydrazine as intermediates [1,2]: hydrazine is formed via a hydrazine synthase complex and then converted to N₂ by a hydrazine dehydragenase enzyme.

The anammox reaction is one of the key biogeochemical processes that leads to the release of geochemically fixed nitrogen as N₂ into the atmosphere. Bacteria growth and study of the anammox reaction is typically performed in bioreactors and lab or industrial environments, but evidence for its natural occurrence below the oxic zone of oceans, such as the anoxic deep water in the Black Sea (the world's largest anoxic basin), has been provided [5].

Keywords: chemistry, biogeochemistry, bioreaction, reaction mechanism, cellular organisms, order Planctomycetales, oceanic nitrogen cycle

References and more to explore
[1] J. Kemsley: Making Dinitrogen. Chem & Eng. News, October 10, 2011, 89 (41), page10.
[2] B. Kartal et al.: Molecular mechanism of anaerobic ammonium oxidation. Nature, 2011, published online October 2, 2011. doi:  http://dx.doi.org/10.1038/nature10453. 
[3] J. G. Kuenen: Anammox bacteria: from discovery to application. Nat. Rev. Microbiol.  April 2008, 6 (4), pp. 320-326 [www.ncbi.nlm.nih.gov/pubmed/18340342].
[4] N. Shivaraman and G. Shivaraman: Anammox - A novel microbial process for ammonium removal. Current Science June 25, 2003, 84 (12), pp. 1507-1508 [www.ias.ac.in/currsci/jun252003/1507.pdf].
[5] M. M. M. Kuypers et al.: Anaerobic ammonium oxidation by anammox bacteria in the Black Sea. Nature April 10, 2003, 422, pp. 608-611.
doi: 10.1038/nature01472.