Seasonal Changes Of Bacterial Flora In Surface Snow From (?)r(?) Mqi Glacier No.1 In The Tianshan Mountains,China

Glacier ice is a unique habitat because it preserves microbial life and past climate records chronologically for hundreds of thousands of years. Microbial cells and other biological material, such as pollen gains, spores, plant debris and insects, associated with dust particles are propelled by the wind from neighbouring and distant places, deposited on the ice surface, and gradually, as snow accumulates, embedded into the deeper ice layers. The microbial studies of deep glacier ice suggested that in-depth fluctuations in cell numbers and microbial composition were related to different dust concentrations and climate changes, could be a potential bio-indicator of paleoclimatology. Therefore, the study of microbial community changes in surface snow is important to reveal the dynamics of correlation between microorganisms and environmental changes in deep ice cores.The seasonal change of microbial numbers and community structure in the surface snow sampled every month from glacier No.l of Tianshan were analyzed by denaturing gradient gel electrophoresis (DGGE), fluorescence microscopy count, microbial culture and the PCR amplification of bacteria 16S rRNA gene. The main results were as follows:1. The distribution of bacteria in surface snow of glacier No.1 in Tianshan demonstrated obvious seasonal characteristic. Total number of bacteria ranged from 3.20 ×103 to 57.85×103 (cells/ml) (Mean,20.56×103; SD,16.17×103; N= 22). The number of bacteria in the spring and summer is lower than that in autumn and winter; the fluctuation of bacterial quantity is larger in autumn and winter. In general, the concentration of bacteria in the snow of 11-20cm layer is higher than that in snow of 0-10cm layer. The amounts of bacteria and cultured bacteria that are positive correlation ship show the same trend related to seasonal changes. There is a certain relationship among the distribution of bacteria, concentration of Ca2+and average temperature of months.2. The seasonal change of bacteria communities was obvious. Cultured bacteria belonged to five phylogenetic groups(Actinobacteria(HGC), Firmicute(LGC),α-proteobacteria,β-proteobacteria,γ-proteobacteria).Including:Arthrobacter, Curtobacterium, Corynebacterium, Frigoribacterium, Microbacterium Rathayibacter, Bacillus, Paenibacillus, Sporosarcina, Sphingomonas, Brevundimonas, Massilia, Psychrobacter and unclassified genus(Representative strain TS0211R and TS0914T), total 15 genera. Actinobacteria(HGC) group commonly existed in all seasons, accounting for 60%of all isolates, followed Firmicute (LGC) group accounted for 17%. There were fewer species of bacteria in Spring and summer (April-August) samples than that in fall and winter season (September-February). Arthrobacter and Sphingomonas were isolated from the samples of all of months; other genera only existed in specific months.3. The results showed the seasonal compositions of bacterial DNA by denaturing gradient gel electrophoresis (DGGE).The cluster analysis of DGGE displayed better regularity in 0cm-10cm snow layer than that in 10cm-20cm snow layer. The structure of bacteria DNA in May to August and October to February displayed high similarity forming two clusters respectively in 0-10cm snow layer. Shannon index (H') showed high bacterial diversity; its peak value appeared in January and May in two snow layer respectively. Sequencing analysis demonstrated Arthrobacter and Bacillus were found in cultivation and DGGE; Crybacterium, Devosia, Janthinobacterium and Cryptococcus were only found in cultivation.There were obvious seasonal change of bacterial diversity and quantity in surface snow of glacier No.1 in Tianshan. The comprehensive picture of microbial shift can be approached by the combined techniques such as fluorescent microscopy, bacterial cultivation and DGGE.