Effect of primary mild stresses on resilience and resistance of the nitrate reducer community to a subsequent severe stress

Authors


  • Present address: Mickael Cregut, UMR INPL-ENSAIA-INRA, Agronomie et Environnement Nancy-Colmar, 2 avenue de la forêt de Haye, BP 172, 54500 Vandoeuvre Les Nancy, France.
    Mélanie Bressan, CEA/Cadarache, DSV-DEVM, UMR 6191 CNRS-CEA- Université de la Méditerranée, Laboratoire d'Ecologie Microbienne de la Rhizosphère, 13108 Saint-Paul-Lez-Durance, France.

  • Editor: Elizabeth Baggs

Correspondence: Laurent Philippot, INRA, University of Burgundy, UMR 1229 Soil and Environmental Microbiology, CMSE, 17, rue Sully, B.P. 86510, 21065 Dijon Cedex, France. Tel.: +33 3 80 69 33 46; fax: +33 3 80 69 32 24; e-mail: philippo@dijon.inra.fr

Abstract

The factors regulating soil microbial stability (e.g. resistance and resilience) are poorly understood, even though microorganisms are essential for ecosystem functioning. In this study, we tested whether a functional microbial community subjected to different primary mild stresses was equally resistant or resilient to a subsequent severe stress. The nitrate reducers were selected as model community and analysed in terms of nitrate reduction rates and genetic structure by narG PCR-restriction fragment length polymorphism fingerprinting. Heat, copper and atrazine were used as primary stresses and mercury at a high concentration as a severe stress. None of the primary stresses had any significant impact on the nitrate reducer community. Although primary stress with heat, copper or atrazine had no effect on the resilience of the nitrate reducer activity to mercury stress, pre-exposure to copper, another heavy metal, resulted in increased resilience. In contrast, the resistance of both structure and activity of the nitrate reducer community to severe mercury stress was not affected by any of the primary stresses tested. Our experiment suggests that the hypothetical effect of an initial stress on the response of a microbial community to an additional stress is complex and may depend on the relatedness of the two consecutive stresses and the development of positive cotolerance.

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