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Letters to Nature

Nature 422, 608-611 (10 April 2003) | doi:10.1038/nature01472; Received 8 November 2002; Accepted 3 February 2003

Anaerobic ammonium oxidation by anammox bacteria in the Black Sea

Marcel M. M. Kuypers1, A. Olav Sliekers2, Gaute Lavik1, Markus Schmid2, Bo Barker Jørgensen1, J. Gijs Kuenen2, Jaap S. Sinninghe Damsté3, Marc Strous4 & Mike S. M. Jetten4

  1. Max Planck Institute for Marine Microbiology (MPI), Department of Biogeochemistry, Celsiusstrasse 1, 28359 Bremen, Germany
  2. Department of Microbiology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands
  3. Royal Netherlands Institute for Sea Research (NIOZ), Department of Marine Biogeochemistry and Toxicology, PO Box 59, 1790 AB Den Burg, The Netherlands
  4. Department of Microbiology, University of Nijmegen, Toernooiveld 1, 6526 ED Nijmegen, The Netherlands

Correspondence to: Marcel M. M. Kuypers1 Correspondence and requests for materials should be addressed to M.M.M.K. (e-mail: Email: mkuypers@mpi-bremen.de).

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The availability of fixed inorganic nitrogen (nitrate, nitrite and ammonium) limits primary productivity in many oceanic regions1. The conversion of nitrate to N2 by heterotrophic bacteria (denitrification) is believed to be the only important sink for fixed inorganic nitrogen in the ocean2. Here we provide evidence for bacteria that anaerobically oxidize ammonium with nitrite to N2 in the world's largest anoxic basin, the Black Sea. Phylogenetic analysis of 16S ribosomal RNA gene sequences shows that these bacteria are related to members of the order Planctomycetales performing the anammox (anaerobic ammonium oxidation) process in ammonium-removing bioreactors3. Nutrient profiles, fluorescently labelled RNA probes, 15N tracer experiments and the distribution of specific 'ladderane' membrane lipids4 indicate that ammonium diffusing upwards from the anoxic deep water is consumed by anammox bacteria below the oxic zone. This is the first time that anammox bacteria have been identified and directly linked to the removal of fixed inorganic nitrogen in the environment. The widespread occurrence of ammonium consumption in suboxic marine settings5, 6, 7 indicates that anammox might be important in the oceanic nitrogen cycle.