高原盐化湖泊沉积物氮代谢特征解析

Characterization for nitrogen metabolism of sediments in highland saline lake

为探索盐碱湖泊微生物群在高盐胁迫下的适应策略,以地处内蒙湖区的岱海沉积物为研究对象,通过宏基因组测序技术揭示其氮代谢微生物的群落结构和功能特征,探究盐胁迫下环境因子对氮代谢功能的影响以及微生物群落构建的驱动机制.结果表明:岱海沉积物氮代谢以异化硝酸盐还原为主要途径,伴随固氮、硝化、反硝化、同化硝酸盐还原、全程氨氧化等5条途径.变形菌门(Proteobacteria)(56.31%~59.19%)、绿弯菌门(Chloroflexi)(8.26%~12.89%)、放线菌门(Actinobacteria)(3.2%~6.4%)是丰度前三的优势菌门,较其他湖泊沉积物优势菌群未见明显差异,但在属水平特异性显著,硫杆菌属(Thiobacillus)(9.8%~15.22%)、未辨别的γ-变形菌纲(unclassified_c_Gammaproteobacteria)(3.49%~4.02%)、硫碱弧菌属(Thioalkalivibrio)(2.69%~3.31%)是参与氮代谢优势菌属.盐度、总氮、总磷及pH值是影响基因丰度的主要环境因子.氮代谢微生物群落构建由确定性过程驱动,在环境过滤作用下6个路径的微生物群落组成各具特色.盐胁迫下嗜盐甲烷氧化菌和硝酸盐还原硫氧化菌主导部分氮代谢过程,将碳氮硫循环耦合起来,造就了岱海沉积物氮代谢过程的特殊性.

In order to explore the adaptation strategy of microbiota in saline-alkali lakes under high salt stress,the community structure and functional characteristics of nitrogen-metabolizing microorganisms in Daihai sediments located in Inner Mongolia were revealed by metagenomic sequencing technology.The effects of environmental factors on nitrogen metabolism and the driving mechanism of microbial community construction under salt stress were explored.The results showed that the nitrogen metabolism of sediments was mainly through nitrate dissimilatory reduction,accompanied by five pathways,including nitrogen fixation,nitrification,denitrification,nitrate assimilatory reduction,and complete ammonia oxidation.Proteobacteria,Chloroflexi,and Actinobacteria were the top three dominant phyla in terms of nitrogen metabolism,which accounted for 56.31%~59.19%,8.26%~12.89%and 3.2%~6.4%of the total microbial community,respectively.There was no significant difference between this microbiota and other sediment of lakes,but the specificity was significant at the genus level.Thiobacillus,unclassified_c_Gammaproteobacteria,and Thiobalkalivibrio were the dominant genera involved in nitrogen metabolism,which accounted for 9.8%~15.22%,3.49%~4.02%and 3.49%~4.02%of the total microbial community,respectively.Salinity,total nitrogen,total phosphorus,and pH were the main environmental factors affecting the abundance of the gene.The assembly of the nitrogen metabolism microbial community was driven by deterministic processes,and the microbial community composition of each of the six pathways was distinctive under the effect of environmental filtering.Halophilic methane-oxidizing bacteria and nitrate-reducing sulfur-oxidizing bacteria dominated part of the nitrogen metabolism process in salt-stressed,which coupled the carbon,nitrogen,and sulfur cycles,resulting in the particularity of the nitrogen metabolism process in sediments of Dai Lake.