Research On Lake Microbial Communities And Function

The hydrosphere is the link connecting of atmosphere,lithosphere and biosphere.Lakes play an important role in the hydrosphere,with numerous types scattered across the globe.Lakes are a crucial ecological type of terrestrial ecosystems and serve as a key ecosystem that responds to climate and environmental changes.They are also considered a hotspot for biogeochemical cycle research.Planktonic microorganisms,which are abundant in number,fast in growth and reproduction,and widely distributed,play a crucial role as producers and decomposers in the water environment.They are an essential component of the global biogeochemical cycle.However,over 95%of microorganisms cannot be cultured in the laboratory.With the rapid development of high-throughput sequencing technology,metagenomics technology can be used to study the community composition,functional metabolism,and material cycle of lake microorganisms without the need for bacteria culturing.Based on 16 S r RNA sequencing data from 51 lakes distributed across three different terrain levels in China,this study conducted metagenomic sequencing on six lakes to investigate the relationship between lake microbial community composition and functional structure,as well as environmental factors.Additionally,the metabolic potential of lake microorganisms and their role in the biogeochemical cycle of elements were explored.Subsequently,metagenomic sequencing was conducted on seven lakes based on 16 S r RNA sequencing data from 24 plain lakes in the middle and lower reaches of the Yangtze River to study changes in the lake microbial community during ecological restoration.The research results are as follows:(1)The findings of this study indicated that while the composition of the dominant microbial community was similar across different terrain levels,microbial abundance varied significantly.The dominant taxa included Actinobacteria,Proteobacteria,Cyanobacteria,Planctomycete,Verrucomicrobia,and Bacteroidetes.Correlation analysis between environmental factors and microbial community structure revealed that elevation and salinity had significant contributions to microbial and functional composition.(2)Metagenomics of six representative lakes revealed the relationships between microbial composition and metabolic processes related to carbon,nitrogen and sulfur cycles.Comparative analysis of genes related to metabolism cycles demonstrated that functional processes such as aerobic respiration,nitrogen assimilation,the mineralization of nitrogen and sulfur had highest metabolic potential in the ecosystems.Analysis of indicator species based on the metabolic process in the carbon,nitrogen and sulfur cycles showed that the microbial community structure is related to the dominant metabolic functions within biogeochemical cycles.Different dominant species play an important and distinct role in lakes with different gradients.Actinobacteria,Cyanobacteria and Proteobacteria were the most important indicator species on the QinghaiTibet Plateau,Yunnan-Guizhou Plateau and the middle and lower reaches of the Yangtze River Plain,respectively.In general,this study explored the functional distribution patterns of the dominant microbial communities in the lakes in biogeocycles.Based on the analysis of specific metabolic processes in the carbon,nitrogen and sulfur cycles,functional redundancy and functional competition were found to exist in the metabolic processes of microbial communities in different habitats.(3)Following ecological restoration,lake water quality significantly improved,and microbial community composition changed markedly.The relative abundance of Cyanobacteria and Planctomycetes in lakes with higher degrees of eutrophication was significantly greater than that in other lakes.The microbial community composition was closely related to total phosphorus,ammonia nitrogen,and chemical oxygen demand,while total phosphorus,total suspended solids,total nitrogen,and chemical oxygen demand were closely related to microbial functional composition.Total phosphorus was most closely related to microbial community and function.Redundancy analysis of dominant microbial community composition and key environmental characteristics revealed that TDS,TP,and NH3-N were positively correlated with the abundance of Cyanobacteria and Planctomycetes,but negatively correlated with Actinobacteria,Bacteroidetes,and Actinobacteria.In summary,the composition of the dominant microbial communities in different ladder lakes was similar,but their abundance significantly differed.Representative indicator species were found in different ladder lakes.The microbial communities in the biogeochemical cycle exhibited both functional competition and redundancy.Ecological restoration has a significant positive effect on aquatic ecosystems.This study provides data to support the research on the composition of microbial communities in typical lake habitats,the interaction between microorganisms and environmental factors,and the biogeochemical cycles in which microorganisms participate.Furthermore,it enriches the research on the underlying mechanism of microorganisms participating in geochemical cycles in the Hydrosphere Microbiology Project.From the microbial level,it highlights the important role of ecological restoration of water environment.