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Sun Dan discussed the carbon storage mechanism of the salt water lake in the Qinghai-Tibet Plateau.
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Abstract: Because of its high altitude, the Qinghai-Tibet Plateau is an important global carbon reservoir, which also shapes the special microbial ecosystem in the region. Under the influence of global warming, the characteristics of the carbon sink on the Qinghai-Tibet Plateau will be changed into a carbon source. It is of great significance to reveal the metabolic potential of microbial community in the carbon and nitrogen cycle and to discover the ecological niche of each population through metagenomics.
- (1) Total environmental DNA of surface water and inshore soil in Lake Namtso was sampled at 30° N 36.223';E 90° 19.731'. Two sets of row squencing data of total environmental DNA of surface water and inshore soil in Lake Namtso respectively are 43 G and 22G obtained by high-throughput sequencing. By metagenomic assembly, 940233 and 735951 continuous overlapped sequences (contigs) ≥1000bp, as well as the total lengths of 2023697642bp and 1410402010bp were obtained, respectively.
- (2) In the composition of surface water microbial community in Lake Namtso, the main phyla are Proteobacteria, Actinobacteria, Fibrobacteria-chlorobia-bacteroidetes group(FCB group) and Cyanobacteria. The main microbial communities in inshore soil of Lake Namtso are Terrabacteria group that is composed of Actinomycetes and Firmicutes, Proteobacteria, FCB group and Acidobacteria. By comparing the community composition of the two biotope, it was found that the proteobacteria participating in the process of aerobic and anaerobic photosynthesis accounted for a higher proportion of the microbial community in the surface water of Lake Namtso, while the Bacteroidetes and Firmicutes with carbon fixation potentia respectively accounted for a higher proportion in the community in surface water and inshore soil of Lake Namtso.
- (3) Through binning of metagenome method, it was gained 60 metagenome-assembled genomes (MAGs) from metagenome in the surface water of the Lake Namtso, including 16 high quality MAGs. Annotate each MAGs and construct genome-wide phylogenetic trees by CVtree. The higher community contents of MAGs in the surface water of Lake Namtso are bin55, bin13, bin40, bin56 and bin12.
- (4) Through the annotation of NCycDB of nitrogen cycle database, it is revealed that bin2 and bin58 have a high degree of nitrogen cycle participation. Through the annotation of the carbohydrate metabolism subsystem, 9 species of carbon fixation bacteria were found that were bin6, bin9, bin30, bin48, bin55, bin57, bin60, bin40 and bin53, as well as the diversity of heterotrophic carbon metabolism. In addition, the dominant bacteria bin13 specially biosynthesise and utilize trehalose, which was the basis of the stable structure of the community. Besides, 7 MAGs carry carbon storage and regulation subsystems that fight carbon starvation in cells by inhibiting glycogen synthesis and assisting peptide transport.
(5)The niches of two Cyanobacteria MAGs were analyzed to reveal how they fixed carbon and converted it into recalcitrant dissolved organic carbon by synthesis of n-acetyl aminoglycans and peptidoglycans. It was also found that two cyanobacteria MAGs were highly adapted to multi-light defense under intense light conditions in the Qinghai-Tibet Plateau, and the protein structure model of ApcE was predicted based on homologous modeling.
(6) Two MAGs with potential for Aerobic Anoxygenic Phototrophic were identified. One of the MAG (bin35), which belongs to the phylum Gemmatimonadetes, is the first example of Aerobic Anoxygenic Phototrophic Bacteria (AAPB) suspected to have been discovered outside the phylum Proteobacteria. According to the analysis of cyanobacteria and AAPB niche, carbon storage mechanism similar to " Microbial Carbon Pump " exists in the surface water of Lake Namtso.
In this paper, we reveal the microbial community composition of surface water and inshore soil in Lake Namtso, the highest altitude saltwater lake in the world. The MAGs were described how to participate in the realization of metabolic function of the community. Through the identification of the maximum ecological niche, the carbon storage mechanism of the saltwater lake on the Qinghai-Tibet Plateau was inferred. It lays a foundation for the further comprehensive study of the actual ecological niches of various microbial groups and the carbon cycle in the Qinghai-Tibet Plateau.
