Microbial Diversity In Snow Of Different Glaciers And Their Relationship With Environment

The glacier environment represents 10%of terrestrial soil ecosystems,is considered extreme because microorganisms must survive prolonged exposure to subzero temperatures and background radiation for geological time scales in a habitat with seriously lack of nutrition.In recent years,microorganisms in glacier attracted high attention of both studies on diversity of life and environment change on earth. However,due to different study regions,little comparative studies of the bacterial diversity in different environment.In addition,much less study is focus on microorganisms in snow,though study on snow has important meaning as on ice core.In order to understand spatial and temporal variations of the bacterial community in snow cover of different type glaciers in China,sampling from maritime glacier Mt. Yulong and inland glacier Mt.Tianshan has been carried out.This work is the first report of the bacterial community in surface snow from these two different types' glaciers.Here,total bacteria counts were established by 4',6'-diamino-2-phenylindole(DAPI) in the snow pack,cultivation-dependent and cultivation-independent approaches,denaturing gradient gel electrophoresis(DGGE), were used to reveal the microbial community structure and diversity.Snow physical, chemical and other environmental variables are measured as well to have a better understanding of the relationship between the bacterial community structure and the environment.The results obtained here were summarized as follows:1.The concentrations of bacteria in snow samples collected from Yulong Mountain were 1.4×10~3～3.13×10~3 cells/ml(mean±standard error,2.1×10~3±0.53×10~3 cells/ml, n=3),lower than the Tianshan Mountain what were 1.03×10~4～1.74×10~4 cells/ml (mean±standard error,1.36×10~4±0.21×10~4 cells/ml,n=3).The total bacterial abundance and cultured bacterial amount have a significant,positive correlation with the concentrations of ions in all snow samples.It suggested that the microorganisms were deposited episodically in glacier with the dust particle.But the particle concentration just is one important factor controlling bacterial abundance,bacteria abundance also influence by other environment factors, including the effect of meltwater washout,UV radiation and temperature and so on.So,lower bacterial amount in some snow samples which have higher concentration of most mineral particles.2.No matter use cultivation-dependent and cultivation-independent approaches, bacterial diversity in Mt.Tianshan snow samples were higher than in Mt.Yulong. The 16S rDNA gene both of cultured bacteria and DGGE band sequenced from Mt.Tianshan belong to following groups:α,β-,γ-proteobacteria, Cytophaga-Flavobacterium-Bacteroides(CFB),High GC and Low GC.In Mt. Yulong,the 16S rDNA genes belong toα-,β-proteobacteria,CFB,High GC and Low GC.The bacterial diversity was influenced by the source and transport of moisture and dust.Bacteria carried by westerlies in winter were distinct from those transported by monsoon in summer.3.The eucaryotic microbial community structures have obvious difference between Yulong mountain snow and East Tianshan mountain snow.The 18S rDNA gene of DGGE band from Yulong mountain snow belongs to Fungi and Cercozoan. But the 18S rDNA gene of DGGE band from East Tianshan mountain snow belonging to the following groups:Viridiplantae,Fungi,Cercozoan,Alveolata and Metazoa.Among these,Viridiplantae and Fungi are dominant groups.And link chemical parameter analysis the relationship between the bacterial community structure and the environment.4.In Mt.Yulong,the bacterial and eucaryotic microbial structure appeared to be similar in snow samples of all depths.But in snow samples of different depths from Mt.Tianshan,microbial structure changed obviously.Bacteria have relationship with ions,and eucaryotic microorganisms have different correlation with ions and bacteria.As snow depth increase,the dominant group changed from Viridiplantae to Metazoa,which is a process from simple to complex.It suggested that the microbial ecosystem in glacier is a particular,dynamic system. Above all,the microbial abundance and diversity in snow of inland glacier were higher than in maritime glacier.The results show that besides environment change, anthropogenic activity and microbial interaction also have a large impact on the snow microbial structure.