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      Anammox bacteria disguised as denitrifiers: nitrate reduction to dinitrogen gas via nitrite and ammonium.

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          Abstract

          Anaerobic ammonium-oxidizing (anammox) bacteria oxidize ammonium with nitrite and produce N(2). They reside in many natural ecosystems and contribute significantly to the cycling of marine nitrogen. Anammox bacteria generally live under ammonium limitation, and it was assumed that in nature anammox bacteria depend on other biochemical processes for ammonium. In this study we investigated the possibility of dissimilatory nitrate reduction to ammonium by anammox bacteria. Physically purified Kuenenia stuttgartiensis cells reduced (15)NO(3) (-) to (15)NH(4) (+) via (15)NO(2) (-) as the intermediate. This was followed by the anaerobic oxidation of the produced ammonium and nitrite. The overall end-product of this metabolism of anammox bacteria was (15)N(15)N dinitrogen gas. The nitrate reduction to nitrite proceeds at a rate of 0.3 +/- 0.02 fmol cell(-1) day(-1) (10% of the 'normal' anammox rate). A calcium-dependent cytochrome c protein with a high (305 mumol min(-1) mg protein(-1)) rate of nitrite reduction to ammonium was partially purified. We present evidence that dissimilatory nitrate reduction to ammonium occurs in Benguela upwelling system at the same site where anammox bacteria were previously detected. This indicates that anammox bacteria could be mediating dissimilatory nitrate reduction to ammonium in natural ecosystems.

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          Author and article information

          Journal
          Environ Microbiol
          Environmental microbiology
          Wiley
          1462-2912
          1462-2912
          Mar 2007
          : 9
          : 3
          Affiliations
          [1 ] Radboud University Nijmegen, Institute for Water and Wetland Research, Department of Microbiology, Nijmegen, 6525 ED, the Netherlands.
          Article
          EMI1183
          10.1111/j.1462-2920.2006.01183.x
          17298364
          5d02ff56-690f-46a2-ba95-912db6f2fd6f
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