Phylogenetic Diversity And Distribution Of Microorganisms In The Tianshan Mountains

Low temperature environment is a special complex ecosytem and it is considered as a center for culture collection.Recently,much progress has been made in terms of microbial research in low temperature environment,especially in cold-adapted microbial ecology.Tianshan area represents a unique environment,low temperature, middle latitude and high altitude,is deemed to a perfect habitat for cold-adapted microorganisms.In this study,snow and frozen soils samples were collected from Tianshan,northwestern China.We investigated the distribution and diversity of the uncultured microorganisms using PCR-DGGE technique,analysed the relationship between microbial communities in different types of samples and discussed the capacity of these organisms to release the greenhouse gases N₂O and CH₄.The major results were obtained as follows:1.Forty-one representative bacterial bands were selected for sequencing and phylogenetic analysis from permafrost.The phylogenetic trees placed these clones into 7 major groups:Acidobacteria,Actinobacteria,Gemmatimonadetes,Chloroflexi, Firmicutes,Proteobacteria and Bacteroidetes,including genera Gemmatimonas, Carnobacterium,Bacillus,Acidobacterium,Arthrobacter,Pseudomonas,Rhodoplanes, Nordella,Herminiimonas,Denitratisoma,Ramlibacter,Flavobacterium, Thermoleiphilum and unidentified bacteria.The Proteobacteria,consisting of theα,β,γ, andεsubdivision,was a clearly dominant group at all depths studied.Of all bacteria, there were 22.7%(9/44)with highest sequence similarity to their closest relatives recovered from other low temperature environments.From this study,it was proposed that permafrost sediments provide a specific ecological niche for diverse microbial lineages.2.Twenty-eight representative archaeal bands were selected for sequencing and phylogenetic analysis from permafrost.The phylogenetic trees placed these clones into three phylogenetic clusters within the two kingdoms,Euryarchaeota and Crenarchaeota. Within the Euryarchaeota,methanogen-related groupâ…¡was most abundant at shallow depth,whereas halobacterium-related groupâ… dominated at greater depths.A Low-Temperature Crenarchaeota group was only detected at 2.5 and 3.0 m.Of all archaea,there were 67.9%(19/28)with highest sequence similarity to their closest relatives recovered from others low temperature environment.This study help to the exploration of cold-adapted archaea in the cold alpine environment,and provided abundant opportunities to clarify cold origin of life and the mechanisms of evolution.3.Thirty-four representative bacterial bands were selected for sequencing and phylogenetic analysis from active layers.The phylogenetic trees placed these clones into 4 major groups:Actinobacteria,Firmicutes,Proteobacteria and Bacteroidetes, including genera Burkholderia,Xanthomonas,Sphingomonas,Pararubellimicrobium, Rudanella,Pedobacter,Dyadobacter,Nocardioides and unidentified bacteria.The most abundant and diverse bacteria were members of Proteobacteria.Of all bacteria,there were 61.8%(21/34)with highest sequence similarity to their closest relatives recovered from others low temperature environment.From this study,it was proposed that cold adaptation bacteria can be preservated on repeated freezing and thawing in active layers.4.Forty representative bacterial bands were selected for sequencing and phylogenetic analysis from snow samples.The phylogenetic trees placed these clones into 3 major groups:Actinobacteria,Proteobacteria and Bacteroidetes,including genera Janthinobacterium,Polaromonas,Acinetobacter,Pseudomonas,Rhodobacter, Nocardioides,Flectobacillus,Hymenobacter and unidentified bacteria.The most abundant and diverse bacteria were members of Proteobacteria.Of all bacteria,there were 47.5%(19/40)with highest sequence similarity to their closest relatives recovered from others low temperature environment.The DGGE pattern showed there were some positive relationship between bacterial species and micro-particles deposited,it suggested the main influence of atmospheric transportation on the microbial distribution in snow and microbial analysis of snow may provide proxy formation for past climates and environments.5.Compare with the bacterial diversity and abundance in snow,active layer and permafrost.We found the bacteria almost wouldn't exchange from each niche.The main reasons caused were the different bacterial sources and different samples formation time.6.Specific-depth distribution of methanogen-related Euryarchaeota groupâ…¡and denitrifying bacteria of the genus Pseudomonas dominated at 1.5 m depth,accompanied with a distinct peak of NH₄-N:NO₃/NO₂-N ratio,implying the potential capacity of these organisms in near-surface permafrost to release the greenhouse gases N₂O and CH₄.7.Some pathogenic bacteria were found in permafrost and snow.Such as Carnobacterium,Burkholderia and Xanthomonas.They will be released accompanied with the permafrost degradation and snow thawing.The data obtained in this study on genetic diversity of uncultured bacteria from the frozen soils and snows in the Tianshan Mountains expand our knowledge on the extent of bacterial diversity in the cold realm and improve our understanding of the biogeographic distribution and function of prokaryotes in alpine environments.