separation of bacteria from soil particles according to sedimentation velocities was first described by Faegri et al. this method is based on two successive centrifugation: first a low speed centrifugation ranging from 500 x g to 1000 z g lasting 2-15 min, respectively, in order to remove (sediment) soil debris, fungal mycelia and heavy soil particle. Optimal conditions for low-speed centrifugation is a compromise between cell recovery efficiency and elimination of contaminating material. A subsequent high-speed centrifugation of the cell-containing supernatant pro