Stimulation of thaumarchaeal ammonia oxidation by ammonia derived from organic nitrogen but not added inorganic nitrogen

Abstract Ammonia oxidation, the first step in nitrification, is performed by autotrophic bacteria and thaumarchaea, whose relative contributions vary in different soils. Distinctive environmental niches for the two groups have not been identified, but evidence from previous studies suggests that act...

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Bibliographic Details
Published in:	FEMS microbiology ecology 2012-04, Vol.80 (1), p.114-123
Main Authors:	Levičnik-Höfferle, Špela, Nicol, Graeme W, Ausec, Luka, Mandić-Mulec, Ines, Prosser, James I
Format:	Article
Language:	eng
Subjects:	Ammonia Ammonia - analysis Ammonia - metabolism ammonia oxidizers Animal, plant and microbial ecology Autotrophic Processes Bacteria - genetics Bacteria - growth & development Bacteria - metabolism Biological and medical sciences Fertilizers - microbiology Fundamental and applied biological sciences. Psychology Microbial ecology mineralization Molecular Sequence Data Nitrification Nitrogen Nitrogen - analysis Nitrogen - metabolism Oxidation-Reduction Phylogeny soil Soil - chemistry Soil Microbiology thaumarchaea Trees Various environments (extraatmospheric space, air, water)
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Summary:	Abstract Ammonia oxidation, the first step in nitrification, is performed by autotrophic bacteria and thaumarchaea, whose relative contributions vary in different soils. Distinctive environmental niches for the two groups have not been identified, but evidence from previous studies suggests that activity of thaumarchaea, unlike that of bacterial ammonia oxidizers, is unaffected by addition of inorganic N fertilizer and that they preferentially utilize ammonia generated from the mineralization of organic N. This hypothesis was tested by determining the influence of both inorganic and organic N sources on nitrification rate and ammonia oxidizer growth and community structure in microcosms containing acidic, forest soil in which ammonia oxidation was dominated by thaumarchaea. Nitrification rate was unaffected by the incubation of soil with inorganic ammonium but was significantly stimulated by the addition of organic N. Oxidation of ammonia generated from native soil organic matter or added organic N, but not added inorganic N, was accompanied by increases in abundance of the thaumarchaeal amoA gene, a functional gene for ammonia oxidation, but changes in community structure were not observed. Bacterial amoA genes could not be detected. Ammonia oxidation was completely inhibited by 0.01% acetylene in all treatments, indicating ammonia monooxygenase-dependent activity. The findings have implications for current models of soil nitrification and for nitrification control strategies to minimize fertilizer loss and nitrous oxide production.
ISSN:	0168-6496 1574-6941