[Advances in extraction and purification of soil microorganism]

For the studies on soil microbial ecology and bio-diversity as well as on the dynamics of C, N, S and P in soil, it is necessary to quantitatively extract microorganism from soil. The recent advances on extraction and purification of microorganism from soil were reviewed in this paper. The procedure for extracting microorganism from soil was comprised of three steps, i.e., soil dispersion, separation and purification. Most bacteria in soil could be successively extracted from soil particles by present techniques such as filtration, centrifugation and elutriation. However, filamentous fungi seem more difficult to be extracted than bacteria, because it is tangled with soil particles. Rotating wire frame, aqueous extraction and membrane filter technique, and low-speed centrifugation were used for extracting filamentous fungi from soil, but the extraction efficiency was rather low and needed to be raised. Aqueous two-phase partitioning system was successfully adopted as a technique for bacteria purification, and it would possibly become a technique suitable for fungi purification. The potential area of research on soil microbial ecology as well as on soil and plant nutrition by using microbial extraction technique was also discussed.