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Anaerobic ammonium oxidation by anammox bacteria in the Black Sea


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.

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Figure 1: Morphology and physiology of anammox bacteria and their role in the marine nitrogen cycle.
Figure 2: Chemical zoning and distribution of anammox indicators across the Black Sea chemocline.
Figure 3: Phylogenetic tree of 16S rRNA gene sequences showing the order Planctomycetales and the position of the anammox-affiliated organisms from the Black Sea (indicated by a rectangle).


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We thank L. Neretin for discussions; the Romanian and Turkish authorities for access to their national waters; the crew of the R/V Meteor for collaboration; S. Krüger, F. Pollehne and T. Leipe (IOW, Warnemünde) for operating the pumpcast and providing the CTD data; J. Eygensteyn, A. Pol, H. op den Camp, K. van de Pas Schoonen and G. Klockgether for analytical assistance. C. Hanfland and the AWI (Bremerhaven) provided the in situ pumps. The investigations were supported by the MPG, the University of Nijmegen, the TU Delft and the DFG. M.M.M.K. was financially supported by the EC Human Potential Programme Research Training Networks Activity (CT-net); A.O.S. was supported by a grant of the ALW; M. Schmid was supported by an EU grant.

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Correspondence to Marcel M. M. Kuypers.

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

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