青藏高原四大特质盐湖微生物的群落形成和环境互作机制研究

Natural salt lake resources are very rich on the Qinghai-Tibet Plateau, and the chemical types of salt lake brine are also obvious different. However, in view of the different hydrochemical subtypes of salt lake, basic theory studies are less related to the microbial diversity, the difference of community structure and the interaction mechanism of environmental adaptation. Salt lake microbes play an important role in the salt lake ecological system of substance circulation, energy exchange, ecological balance and maintaining participation. Based on the regional advantages of salt lake resources, this project will carry out the microbial diversity, the community structure and the microbial community formation in four hydrochemical subtypes of salt lake (e.g. carbonate subtype, sodium sulfate subtype, magnesium sulfate and chloride subtype) with the high-throughput sequencing and metagenomics technology. Furthermore, the environment interactions mechanism with functional microbial communities will expound by the molecular coupling between special energy metabolism and environmental adaptation. By mining extremely halophilic bacterium, we plan to discuss the gene expression and difference expression, the regulating network of metabolic pathways and the molecular mechanisms of salt-environment adaptation under the salt-shock model, according to the comparative transcriptome analysis. This study will provide solid theoretical references for the subject development of salinology, and the comprehensive development and rational utilization of salt lake biological resources.

青藏高原极端盐湖资源丰富，盐湖卤水的化学类型明显差异，然而针对不同化学类型盐湖的微生物多样性、群落结构差异和盐境适应互作机制等相关基础理论研究较少。在盐湖生态系统的物质与能量循环、演替和维持中，盐湖微生物发挥了重要的参与作用。本项目依托青藏高原地区的盐湖资源优势，借助高通量测序和宏基因组学技术深入解析青藏高原四大卤水特征盐湖(碳酸盐型、硫酸钠亚型、硫酸镁亚型和氯化物型)的微生物多样性、群落结构差异与形成规律，探讨关键功能微生物群的特殊能量代谢及与环境适应的分子耦合和互作机制；通过挖掘盐湖极端嗜盐菌资源，采用比较转录组学技术揭示嗜盐模式菌株在盐激条件下的基因表达差异、网络代谢通路调控及盐境适应的分子机制。此为盐湖学(Salinology)学科的发展、盐湖生物资源的综合开发和合理利用提供详实的参考依据。

青藏高原是中国最密集的极端环境湖泊群分布区, 湖泊类型和水化学特征多样化。然而, 涉及青藏高原不同水化学特征湖泊的细菌群落组成与多样性差异的系统研究较少。本文以青藏高原4类典型水化学特征湖泊(即氯化物型/MgSO4亚型/Na2SO4亚型/碳酸盐型, 共计32个样点)为研究对象, 借助Illumina测序16S rRNA基因(V3‒V4区)分析细菌的多样性、群落结构的组成以及环境因素的制约关系。结果表明:多样性指数为碳酸盐型＞Na2SO4亚型＞MgSO4亚型＞氯化物型。分类地位明确的细菌共计45门81纲1,148属(OTU 52,031个), 优势类群主要有变形菌门、拟杆菌门、厚壁菌门、疣微菌门、浮霉菌门、放线菌门、梭杆菌门、酸菌门、异常球菌-栖热菌门以及俭菌总门。Na2SO4亚型与碳酸盐型组样本相似类聚, 优势属Aquiflexum、Haliea与Luteolibacter的聚集分布与HCO3-浓度、pH值和海拔高度相关; 而氯化物型组与少数MgSO4亚型组样本相似聚集分布, 优势属Bacillus和Oceanobacillus的聚集分布与SO42-浓度正相关; 优势属Pseudomonas、Lactococcus和Acinetobacter等的聚集分布与总盐度、主要离子(Mg2+、Cl-、Na+与K+)和温度相关。中度嗜盐菌是柴达木盆地极端湖泊的优势类群，其中Bacillus属43株和Halomonas属26株。通过设置无盐组NS(0 M NaCl)、中盐组MS(1.5 M NaCl )和高盐组HS (2.5 M NaCl )，培养H. campaniensis XH26菌株进行转录组学分析。转录组测序(n=3/组)共注释操纵子748个(涉及2182个基因)，转录起始-终止位点941个，预测新转录本456个，上调基因385个和下调基因326个(涉及245个KEGG通路)。Ectoine的生物合成与Asp(或天冬氨酸半缩醛)、上游氨基酸代谢网络(Asn、Glu、Gln和His)以及三羧酸循环(琥珀酸、延胡索酸和草酰乙酸)密切相关，此为后续四氢嘧啶合成途径的优化和代谢通路的整合设计提供重要的参考依据。