Diversity And Physiological Characteristics Of Culturable Microbes In Qinghai-tibet Plateau Permafrost Region

Permafrost is a ecosystem characterized by extremely cold and oligotrophic conditions. Such an unique ecosystem benefits the preservation of living organisms and biological macro-molecules. Therefore, it is regarded as "living fossils" in the study of the evolution of earth’s environment and life. In this study, fifteen permafrost samples (0.5-9.75m) at different depth intervals from the Qinghai-Tibet Plateau were collected as experimental materials. We employed traditional culture-dependent method combined with DNA molecular method to analyze the culturable microbial diversity, quantity, colony morphology, Gram-stain and pigmentation. Moreover, the range of growth temperature, salt and pH tolerance, as well as extracellular enzyme activities at low temperature were tested. Such extracellular enzyme activities include amylase, protease, lipase and cellulase. The main results are as follows.1. The culturable fungus were identified by ITS sequence and divided into two groups, Ascomycota and Basidiomycota. The quantity of culturable bacteria was up to10+-107CFU/g dry soil, and the culturable bacteria were classified into five phylum, that is, Actinobacteria, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Firmicutes; seventeen genera, such as, Arthrobacter、Pseudomonas、Sphingomonas、Brevundimonas、Bacillus、 Paracoccus、Acinetobacter、Cryobacterium、Psychrobacter、Salinibacterium、Microbacterium、 Rhodococcus、Dietzia、 Kocuria、 Phyllobacterium、Massilia、Variovorax. Among them, the most abundant phylum was Actinobacteria, followed by Gammaproteobacteria. The quantity and diversity of culturable bacteria at different depth intervals from the Qinghai-Tibet Plateau permafrost showed some similarities. Arthrobacter was the dominate group that distributed at the all depth intervals. Moreover, the differences were also existed. With increasing of the permafrost sample depths, the quantity and diversity of the culturable bacteria were both decreased.2. The culturable bacteria from Qinghai-Tibet permafrost samples was mainly made up of Gram-positive bacteria. The size of detected cells was extremely small and mainly rods. Of all these culturable bacteria,71%could produce pigments and became colorful, such as peach, lemon yellow, orange and so on;24%were psychrotolerant bacteria but psychrophilic strains were rare;49%of the bacterial strains showed a strong salt resistance up to11%of NaC1concentration at low temperature. In addition,73%of the strains showed a strong tolerance to alkaline, and could survive under a extreme alkali condition (pH13) at low temperature. These bacterial strains also had extracellular enzyme activity in low temperature condition.64%strains could produce extracellular lipase, followed by29%producing extracellular amylase. Strains producing extracellular cellulase and extracellular protease accounted for13%and9%, respectively.In conclusion, the diversity of culturable fungi is low as it is hard to culture and only separates in superficial samples;the culturable bacteria communities from different samples were similar, Arthrobacter distributed in all depths samples. With increasing depth of permafrost soils, the quantity and diversity of the culturable bacteria are both decreased. The study of phenotypic characteristics illustrates the ability of bacteria adapt to the environment. Moreover, it may provide a theoretical basis and scientific support for further study in low temperature microbe.