Shifts between Nitrospira- and Nitrobacter-like nitrite oxidizers underlie the response of soil potential nitrite oxidation to changes in tillage practices

Authors

  • E. Attard,

    1. Laboratoire d'Ecologie Microbienne, Université de Lyon, Université Lyon 1, UMR CNRS 5557, USC INRA 1193, bât. G. Mendel, 43 boulevard du 11 novembre 1918, 69622 Villeurbanne, France.
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  • F. Poly,

    1. Laboratoire d'Ecologie Microbienne, Université de Lyon, Université Lyon 1, UMR CNRS 5557, USC INRA 1193, bât. G. Mendel, 43 boulevard du 11 novembre 1918, 69622 Villeurbanne, France.
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  • C. Commeaux,

    1. Laboratoire d'Ecologie Microbienne, Université de Lyon, Université Lyon 1, UMR CNRS 5557, USC INRA 1193, bât. G. Mendel, 43 boulevard du 11 novembre 1918, 69622 Villeurbanne, France.
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  • F. Laurent,

    1. ARVALIS Institut du Végétal, 91720 Boigneville, France.
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  • A. Terada,

    1. Department of Environmental Engineering Technical University of Denmark, Miljoevej, Building 113, DK-2800 kgs. Lyngby, Denmark.
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  • B. F. Smets,

    1. Department of Environmental Engineering Technical University of Denmark, Miljoevej, Building 113, DK-2800 kgs. Lyngby, Denmark.
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  • S. Recous,

    1. INRA, UR1158 Unité d'Agronomie, rue F. Christ, F-02000 Laon, France.
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  • X. Le Roux

    Corresponding author
    1. Laboratoire d'Ecologie Microbienne, Université de Lyon, Université Lyon 1, UMR CNRS 5557, USC INRA 1193, bât. G. Mendel, 43 boulevard du 11 novembre 1918, 69622 Villeurbanne, France.
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  • Present addresses: UMR614 INRA-URCA FARE, 2 esplanade Roland Garros, 51000 Reims, France; Fondation pour la recherche sur la biodiversité FRB, 57 rue Cuvier, 75005 Paris, France.

*E-mail xavier.leroux@fondationbiodiversite.fr; Tel. (+33) 1 40 79 57 04; Fax (+33) 1 40 79 56 63.

Summary

Despite their role in soil functioning, the ecology of nitrite-oxidizing bacteria, NOB, and their response to disturbances such as those generated by agricultural practices are scarcely known. Over the course of 17 months, we surveyed the potential nitrite oxidation, PNO, the abundance of the Nitrobacter- and Nitrospira-like NOB (by quantitative PCR) and the community structure of the Nitrobacter-like NOB (by PCR-DGGE and cloning-sequencing targeting the nxrA gene) in soils for four treatments: after establishment of tillage on a previously no-tillage system, after cessation of tillage on a previously tillage system, and on control tillage and no-tillage systems. Key soil variables (moisture, organic carbon content and gross mineralization – i.e. ammonification – measured by the 15N dilution technique) were also surveyed. PNO was always higher for the no-tillage than tillage treatments. Establishment of tillage led to a strong and rapid decrease in PNO whereas cessation of tillage did not change PNO even after 17 months. PNO was strongly and positively correlated to the abundance of Nitrobacter-like NOB and was also strongly related to gross mineralization, a proxy of N-availability; in contrast, PNO was weakly and negatively correlated to the abundance of Nitrospira-like NOB. Selection of a dominant population was observed under no-tillage, and PNO was loosely correlated to the community structure of Nitrobacter-like NOB. Our results demonstrate that Nitrobacter-like NOB are the key functional players within the NOB community in soils with high N availability and high activity level, and that changes in PNO are due to shifts between Nitrospira-like and Nitrobacter-like NOB and to a weaker extent by shifts of populations within Nitrobacter-like NOB.

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