1. Department of Microbiology, Swedish University of Agricultural Sciences (SLU), P.O. Box 7025, 750 07 Uppsala, Sweden
2. Department of Soil and Water, Faculty of Agriculture, Sabha University, P.O. Box 19332, Sabha, Libya
3. Department of Soil and Environment, Swedish University of Agricultural Sciences (SLU), P.O. Box 7014, 750 07 Uppsala, Sweden