Bacterial Diversity In Snowpack On The Tibetan Plateau & Its Adjacent Regions And Their Environmental Significance

The origin and composition of microbial populations which preserved in glacier were influenced by local climate conditions and global atmospheric circulation. Snow and glacier ice are two interrelate ecosystems. Glacier is formed from snow as a result of gradual compression and transformation into ice. Therefore, glacial surface snow and deep ice core research is complement each other. So, snowpack provides an ideal model to obtain accurate data and study the bacterial characterization and its relationship between environments. Four snowpack were collected from Tianshan NO.1 glacier, Laohugou glacier, Zhadang glacier and Demula glacier along the north-south transect of the Tibetan Plateau and its adjacent regions. Bacterial diversity and cell abundance in the snow of the four snowpack were investigated through culture-dependent combined with culture-independent techniques (16S rRNA genes clone library) and Epifluorescence Microscopy technology. This study aimed to assist with the explanation of the seasonal and spatial variations of bacterial diversity and their environmental significance.Ⅰ. Bacterial characterization of the four snowpack1. In the four snowpack, total bacterial abundance, culturable bacterial concentration, particle and major ionic (Ca2+, Mg2+) was higher at the northern glaciers than at the southern ones. Total bacterial concentration was estimated to range of 2.85×104-3.11×105cells ml-1, population of culturable bacteria was to range of 2-1748 CFU ml-1 in snowpack of Tianshan glacier. Total bacterial concentration was estimated to range of 4.16×104-2.29×103cells ml-1, population of culturable bacteria was to range of 1-1046 CFU ml-1 in snowpack of Laohugou glacier. Total bacterial concentration was estimated to range of 1.61×104-8.09×104cells ml-1, population of culturable bacteria was to range of 1-1137 CFU ml-1 in snowpack of Zhadang glacier. Total bacterial concentration was estimated to range of 2.98×104-9.14×104cells ml-1, population of culturable bacteria was to range of 5-201 CFU ml-1 in snowpack of Demula glacier.The positive correlation between concentrations of total bacteria and culturable bacteria and major ions (Ca2+ Mg2+) may indicate that atmospheric transport and deposition of microorganisms in the Tibetan Plateau are dominated via particulate binding.2. Culturable bacterial diversity in the snowpack varied at different glaciers.1) The dominant bacterial group is different. In the snowpack of the Tianshan NO.1 glacier, the dominant bacterial group isβ-Proteobacteria. In the snowpack of Laohugou glacier, the dominant bacterial group is Firmicutes and Bacteroidetes. In the snowpack of Zhadang glacier, the dominant bacterial group is Firmicutes. In the snowpack of Demula glacier, the dominant bacterial group is Actinobacteria. 2) The culturable bacterial genera are different. The obtained sequences belonged to 22 genera, only 5 genera which are Arthrobacter, Subtercola, Bacillus, Caryophanon, Polaromonas occurred in all glaciers.3) The bacterial diversity in the snowpack at different glaciers was related to the surrounding environments. In the snow of Tianshan NO.1 glacier and Laohugou glacier preserved more bacteria closely related to soil than the other glaciers. However, in Demula glacier more bacteria closely related to aquatic environments.3. Bacterial community structure in the snowpack varied at different glaciers. 1) The constructed universal 16S rRNA gene clone libraries results showed that the obtained sequences belong to a-,β-, y-Proteobacteria, Actinobacteria, Firmicutes, Bacteroidetes, Cyanobacteria. The dominant bacterial group isβ-Proteobacteria (59%-71%).2) The bacterial community structure varied in different glaciers. Firmicutes only present in the snowpack of Zhadang glacier, and Cyanobacteria only present in the snowpack of Laohugou glacier and Zhadang glacier.3) The OTU in different glacier is different. Total of 64 OTU inβ-Proteobacteria only 12 occurred in all glaciers, total of 26 OTU in Bacteroidetes only 5 occurred in all glaciers.4) The bacterial community diversity is different. In the snowpack of Tianshan NO.1 glacier the diversity is the highest, while Laohugou glacier is the lowest and Zhadang and Demula glacier are in above range.5) The bacterial diversity in the snowpack at different glaciers was related to the surrounding environments. The snowpack of Tianshan NO.1 glacier preserved more bacteria closely related to soil than the other glaciers.Ⅱ.Monsoon and non-monsoon variations of bacterial characterization in the snowpack of Zhadang glacier1. Total bacterial abundance, culturable bacterial concentration, particle and major ionic (Ca2+, Mg2+) was higher in non-monsoon than in monsoon in the snowpack of Zhadang glacier. In monsoon and non-monsoon, the total bacterial abundance was 2.16×104cells ml-1 and 5.87X104 cells ml-1, respectively. The culturable bacterial concentration was 112 CFU ml-1 and 219 CFU ml-1, respectively. The particle concentration was 1.0×x10-5ml-1 and 10.0×105ml-1, respectively. Ca2+ concentration was 20ng g-1 and 123.92ng g-1, respectively. Mg-2 concentration was 264.62ng g-1 and 1064.31ng g-1, respectively.2. Seasonal variations of culturable bacteria. The dominant bacterial group was a-Proteobacteria,β-Proteobacteria, Firmicutes in monsoon, while in non-monsoon the dominant bacterial group is Firmicutes. 3. Seasonal variations of bacterial community structure.1) The obtained sequences from constructed 16S rRNA gene clone libraries were classified into seven groups:α-,β-, y-Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, Cyanobacteria, and P-Proteobacteria (56% and 59% ) was the dominant bacterial group.2) The bacterial group had obvious seasonal variations. The bacterial group had season-specific, such as the Cyanobacteria only obtained in monsoon season while Firmicutes only presented in non-monsoon.3) More bacteria originated from aquatic environment in monsoon season, while some bacteria were related to cold environments and soils in non-monsoon season.4) Bacterial community diversity in monsoon is lower than that in non-monsoon.Above all, bacterial groups, genera and species using different technique (16SrRNA gene clone libraries and cultural bacteria) were diverse from the seasonal and spatial of snowpack. The results indicate that the seasonal and spatial variations of abundance and bacterial diversity were corresponded to the local climate conditions and global atmospheric circulations.