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 regions. The conversion of nitrate to N2 by heterotrophic bacteria (denitrification) is believed to be the only important sink for fixed inorganic nitrogen in the ocean. 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 bioreactors. Nutrient profiles, fluorescently labelled RNA probes, 15N tracer experiments and the distribution of specific 'ladderane' membrane lipids 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 settings indicates that anammox might be important in the oceanic nitrogen cycle.
Kuypers
Marcel M M
MM
Max Planck Institute for Marine Microbiology, Department of Biogeochemistry, Celsiusstrasse 1, 28359 Bremen, Germany. mkuypers@mpi-bremen.de
Sliekers
A Olav
AO
Lavik
Gaute
G
Schmid
Markus
M
Jørgensen
Bo Barker
BB
Kuenen
J Gijs
JG
Sinninghe Damsté
Jaap S
JS
Strous
Marc
M
Jetten
Mike S M
MS
D000693:Anaerobiosis; D001421:Bacteria, Anaerobic / Q000235:genetics / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012623:Seawater / Q000737:chemistry*
D009573:Nitrites; D000644:Quaternary Ammonium Compounds; D012336:RNA, Ribosomal, 16S; D009584:Nitrogen; D010100:Oxygen