1. Department of Microbial Ecology, University of Lund, Ecology Building, Helgonävagen 5, S‐223 62 Lund, Sweden
2. Equip de Microbiologie Forestière, Centre de Recherches Forestieres de Nancy, INRA, Champenoux 54280, France
3. Department of Molecular and Cell Biology, University of Aberdeen, Marischal College, Aberdeen AB9 IAS, UK
4. Department of Plant and Soil Science, University of Aberdeen, Meston Building, Aberdeen AB9 2UE, UK