青藏高原小柴旦盐湖微生物群落结构及多样性

Microbial Community Structure and Diversity of Xiaochaidan Salt Lake on the Tibetan Plateau

通过探究小柴旦盐湖微生物群落结构与多样性,为盐湖微生物资源的开发利用和生态保护提供重要的理论参考依据。利用Illumina Mi Seq测序平台对小柴旦盐湖细菌和古菌的16S rRNA基因(V3~V5区)进行高通量测序,获得细菌和古菌的物种注释OTU(Operational Taxonomic Units)数目分别为870和410,其中分类地位明确的细菌有18门、24纲、135属,古菌2门、4纲、22属。细菌优势类群依次是厚壁菌门(Firmicutes,34.05%)、变形菌门(Proteobacteria,32.91%)、拟杆菌门(Bacteroidetes,18.01%)和蓝细菌门(Cyanobacteria,8.46%);优势种群依次是芽孢杆菌属(Bacillus,21.53%)、Chloroplast-norank(6.65%)和海杆菌属(Marinobacter,4.05%)。古菌的优势类群和优势种群主要是未确定分类地位的沃斯古菌门(Woesearchaeota DHVEG-6,80.84%),相关的系统分类学尚需深入研究。小柴旦盐湖微生物的种群结构复杂、类群丰富,细菌Shannon多样性指数(4.77±0.45)显著高于古菌(2.79±0.45),且存在大量的新种资源。

Unique halophilic bacteria and archaea with rich species genetic diversity inhabit Xiaochaidan Salt Lake and play a critical role in material circulation,energy flow and ecosystem succession of the salt lake ecosystem. Xiaochaidan Salt Lake is located in the Qinghai-Tibetan Plateau of China and is a representative extreme hypersaline ecosystem,yet its microbial diversity has remained unknown. In this study,we investigated the microbial community structure and diversity in the water and sediment of Xiaochaidan Salt Lake via high-throughput sequencing of the V3-V5 regions from 16 S rRNA gene of archaea and of bacteria based on an Illumina platform. The objective was to provide a theoretical reference to support environmental protection and microbial resource utilization of the lake.In July 2015,mixed samples of water and sediment were collected from four sampling sites in Xiaochaidan Salt Lake（ X1,X2,X3 and X4）. The sample sites were spaced at 100 m intervals and samples were collected at depths of 10,20,30 and 40 cm. Ion chromatographic analysis was used to determine total dissolved salt（ TDS,108. 82-113. 84 g/L）,total organic carbon（ TOC,3. 12-4. 28 g/L）,total nitrogen（ TN,0. 12-0. 32 g/L）and pH（ 7. 8-8. 2）. Based on hydrochemical characteristics,Xiaochaidan Salt Lake was characterized as a magnesium sulfate-subtype brine lake. A total of 147,410 sequences were obtained for bacteria and 118,216 sequences for archaea. A high diversity of OTUs（ operational taxonomic units） were detected for bacteria（ 870） and archaea（ 410） ： 18 phyla,24 classes and 135 genera of bacteria and 2 phyla,4 classes and 22 genera of archaea.Firmicutes（ 34. 05%） was the dominant bacterial phyla,followed by Proteobacteria（ 32. 91%）,Bacteroidetes（ 18. 01%）,Cyanobacteria（ 8. 46%）,Actinobacteria（ 2. 39%） and Chloroflexi（ 1. 09%）. The dominant bacterial genus was Bacillus（ 21. 53%）,followed by Chloroplast-norank（ 6. 65%）,Marinobacter（ 4. 05%）,Oceanobacillus（ 3. 82%）,Lactococcus（ 3. 65%） and Pseudomonas（ 3. 46%）. The dominant taxa of archaea was unclassified Woesearchaeota DHVEG-6（ 80. 84%） with no clear taxonomic classification. The microbial community in Xiaochaidan Salt Lake is abundant and complex,with high species richness. The Shannon diversity（ 4. 77 ±0. 45）,Ace and the Chao1 indices of the bacterial community were much higher than the indices of the archaeal community（ Shannon diversity index,2. 79 ± 0. 45）. Many new species remain unknown in Xiaochaidan Salt Lake,particularly in the Woesearchaeota phylum,and need further study. This research,based on high-throughput sequencing,comprehensively explored and characterized the microbial resources in Xiaochaidan Salt Lake and the findings will support further exploitation of the microbial resource.