| As an important part of the earth hydrosphere,lake ecosystem can provide abundant water resources for human beings.Microorganism is an important part of lake ecosystem and plays an important role in the circulation of lake chemical elements,especially the circulation of carbon,nitrogen and phosphorus.Therefore,the study of lake microorganism has important ecological significance.Hulun Lake is the largest lake in Inner Mongolia Autonomous Region.It is an important ecological barrier in northern China and plays an important ecological role in regional environmental protection.The microorganisms in the lake are an important part of the lake ecosystem.However,the microbial community characteristics of the water system of Hulun Lake and the response mechanism of the water microorganisms to environmental factors are still unclear.Therefore,we studied the microbial community in Hulun Lake by the high-throughput sequencing of V3-V4 region of 16 S r RNA gene and combined analysis with environmental factors in order to reveal the status of microbial resources in the lake and the adaptation mechanism of microorganisms to specific environment in Hulun Lake.The results are as follows:(1)T test results shown that the physical and chemical indexes of the surface water of Hulun Lake are different in summer and winter.The water temperature and pH in summer are significantly higher than those in winter,and the DO(Dissolved Oxygen)and COD(Chemical Oxygen Demand)in winter are significantly higher than those in summer.(2)A total of 9,575,501 effective sequences were detected from 108 samples in the summer of 2018 by high-fluence sequencing analysis.Classification and labeling showed that a total of 55 phyla,144 classes,202 orders,363 families,652 genera and 219 species were detected,among which the dominant flora at phylum level were:Proteobacreria,Actinobacteria,Bacteroidetes,Verrucomicrobia,Planctomycetes,Cyanobacteria;In the winter of 2018 samples of 126 determine the total of 13896677 valid sequence,classification annotations shows detected 64 phyla,165 classes,218 orders,386 families,740 genera,222 species,including the advantage bacterium group at the phylum level for:Proteobacreria,Actinobacteria,Bacteroidetes,Firmicutes,Cyanobacteria.(3)The diversity analysis based on OTU level showed that the richness and evenness of sediments were higher than that of water bodies.Through LEf Se analysis,we identified 8 and 3 biomarkers in summer lake water and sediments respectively.In winter,14 and 6 biomarkers were identified in lake water and sediment,respectively.(4)Functional prediction showed that metabolic pathways and environmental information processing were the most important metabolic pathways.At Level 2,the main functions of sediments and lake water were carbohydrate metabolism and amino acid metabolism.At Level 3,we found that the main function was nitrogen metabolism pathway,which was significantly higher in sediments than in water samples.(5)The analysis of environmental contribution showed that temperature and dissolved DO were the environmental factors with the highest connectivity.Redundancy analysis showed that temperature and pH were the main factors affecting the microorganisms in summer,and DO was the main factor affecting the microorganisms in winter.In conclusion,the results of this paper indicated that the diversity of microbial community in the sediments of Hulun Lake is higher than that in the water body.In addition,temperature,DO and pH were the main factors affecting the microbial community distribution in Hulun Lake.This study revealed the characteristics of the microbial community in the water system of Hulun Lake and the influence of environmental factors on the bacterial community in Hulun Lake,which provided a new idea for the study of the relationship between environmental factors and the distribution of bacterial community in freshwater ecosystem,and also provided a theoretical basis for the environmental monitoring and protection of the lake. |
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