青藏高原多年冻土微生物的培养和计数

Culturing and Counting the Microbial Cells inPermafrost on the Tibetan Plateau

以青藏高原腹地北麓河流域的两个6m钻孔为对象,对多年冻土中保存的微生物进行初步培养和总数测定,并分析了微生物与土壤环境之间的关系.结果表明,两个钻孔中可以培养的微生物数目在3.6×106～5.0×102之间;随着深度增加,冻土年代递增,可以培养的数目显著减少.表层冻土属于季节冻土,可培养的微生物种群较多.总的土壤微生物数目(包括可以培养和不能培养的微生物)随深度递减,两个孔在3.8×109～1.0×107之间.相关性分析表明,土壤中可以培养的微生物以及总的微生物与土壤的pH值、电导率、总有机质和全氮没有显著的相关关系,而与土壤深度关系密切.两个钻孔间的地表植被虽然差异明显,但从可培养的微生物数量和土壤微生物总数比较看来,两孔间没有明显的不同.

Permafrost is one of extreme environments, which limits the life while maintains a long-term stability in temperature, water, nutrients and gas, so it is a better medium for studying the life in the extreme environment. The Tibetan plateau possesses the most of high-altitude permafrost in the world, with higher temperature and less depth as compared with that in arctic and Siberia. It is viewed as a 'magnifier' or 'accelerator' of global climate change, so it is important to study the microbiological ecology, diversity and physiology in permafrost regions. Two cores, about 6 m in depth, were drilled in the Beilu River basin within the hinterlands of the Tibetan Plateau. The surface parts of the extracted cores were immediately trimmed off with a sterile knife, and core sections were placed in pre-sterilized aluminum tins, sealed and kept frozen during storage and transport. The samples were kept at -18℃ before experiment. More than 40 sections were obtained along the core length at a regular interval. Culturable microorganisms in the soils of different depths were cultured with PYGV agar media at 4℃ and 20℃. Accordingly, the total microbial number in soils was counted after staining fluorescence material, DAPI (4′, 6-diamidino-2-phenylindole). At the same time, pH value, electro-conductance rate, total organic carbon and total nitrogen in different soils were analyzed with regular methods. Generally, the soils show alkaline property (pH 8.0～9.2), low organic carbon (between 0.2%～1.3 %), low total nitrogen content (0.007%～0.11%) and high electron-conductance rate. It is found that there are 3.6×10~6～5.0×10~2 (cfu/g dw) viable microbial communities in the plateau. The number of colony forming unit is greater in the active layer than in the stable layer, and gradually decreases with depth. The total number of microorganisms shows the same trend as the viable microbes, ranging from 3.8×10~9 to 1.0×10~7 cell(g dw)~{-1}. Statistically analysis indicates no significant relationship between soil physical-chemical properties and microorganisms in soils, except an obviously negative relationship between the number of microorganisms and the permafrost depth. There is no significant difference between the two cores. It is necessary to further study the illustration of the species diversity, ecology of these viable microorganisms and the relationship with permafrost environment.