Study On Molecular Ecology Of Toxigenic Cyanobacteria In Different Trophic Lakes Of Yunnan Plateau

The lake ecosystem in nature is closely related to human health and social and economic development.In recent years,with the rapid development of urbanization and industry and agriculture,the problem of eutrophication of lake has become more and more serious.The eutrophication of lakes leads to the destruction of aquatic ecosystem,and the toxic cyanobacteria blooms produce algal toxins that directly endanger human life and health.This study takes the different trophic lakes(Xingyun Lake and Fuxian Lake)in Yunnan Plateau as the research objects.The environmental factors of the two lakes were analyzed to evaluate the influence on water quality.The genetic diversity and abundance of toxigenic cyanobacteria in these two lakes were investigated by qualitative and quantitative analysis based on different cyanobacteria toxin synthesis genes.The microbial community structure,differentially expressed genes and cyanobacterial toxin synthesis gene were analyzed by macrotranscriptomics in the two lakes during algal blooms and non-algal blooms.It provides theoretical basis for scientific evaluation of the ecological status of the lake,the control of cyanobacteria blooms and environmental management of the lake.The main research results are as follows:1.All environmental indicators of Xingyun Lake's water samples during wet period,normal water period,dry period and sediment samples except water temperature are significantly higher than those of Fuxian Lake.The eutrophication of Xingyun Lake is serious,and the eutrophication of Fuxian Lake is relatively light.The content of chlorophyll a was significantly positively correlated with other environmental factors except water temperature.2.Total microcystis 16 s r RNA,microcystin synthesis gene mcy A,anatoxin synthesis ana C,and saxitoxin synthesis gene sxt A genes were detected in the water bodies of Xingyun Lake and Fuxian Lake,but only the microcystin-producing mcy A gene and total Microcystis 16 s r RNA were detected in the sediments of Xingyun Lake.Microcystins in the two lakes are mainly produced by toxin-producing cyanobacteria of the Microcystis,and saxitoxin are mainly produced by toxin-producing cyanobacteria of Anabaena.Anatoxins are mainly produced by toxin-producing cyanobacteria of Oscillatoria in Fuxian Lake,and mainly produced by toxin-producing cyanobacteria of Aphanizomenon in Xingyun Lake.3.Analysis of the gene abundance of toxin-producing cyanobacterial toxin genes in different periods found that the abundance of microcystin and anatoxin toxinproducing cyanobacteria in the eutrophic Xingyun Lake was significantly higher than that in the oligotrophic Fuxian Lake.The abundance of toxin-producing Microcystis is the highest in the two lakes.The abundance of saxitoxin toxin-producing cyanobacteria in Fuxian Lake is higher than that in Xingyun Lake.Based on the analysis of different seasons,the abundance of microcystins was the highest in wet period.The anatoxin genes and saxitoxin genes are different in different periods.At the same time,different cyanobacteria toxin-producing genes have different correlations with environmental factors,and the anatoxin-producing ana C gene is more affected by environmental factors.4.The analysis of the microbial communities in the two lakes during the wet and dry periods revealed that the microbial community diversity in the oligotrophic Fuxian Lake is more abundant than that in the eutrophic Xingyun Lake.The difference in the main microbial communities between the two periods in Xingyun Lake is relatively small.The highest abundance are Cyanophyta,Microcystis,and Microcystis aeruginosa in Xingyun Lake.There are differences in the main microbial communities in the two periods of Fuxian Lake.Proteobacteria,Clostridium,and Clostridium cellulosum were the highest abundances in the water period,and Cyanobacteria,Proteus,and Cyanothece were the highest abundances in the dry period.5.Annotation of the plankton functions of the two lakes during the wet and dry periods found that the two lakes mainly carry out biological functions and metabolic pathways related to respiration during the wet and dry periods of the two lakes.Through the functional annotation of differential genes,it is found that the main differential functions of the two lakes during the wet and dry periods come from the enzymes and organelles related to photosynthesis.Therefore,the photosynthesis in the wet period is stronger than that in the dry period.At the transcription level,the expression of the three cyanotoxin-producing genes in Xingyun Lake was higher than that of Fuxian Lake in the wet period,and the saxitoxin-producing genes in the dry period were slightly lower than in Fuxian Lake.The expression levels of cyanobacteria toxin-producing genes are different in different periods.6.The correlation between the microbial community and the gene abundance of cyanobacterial toxins indicated that the populations of the two lakes differed significantly during the wet and dry periods.The differences in the populations of the two lakes during the dry period were small.The gene abundances of mcy A,ana C,and sxt A are positively correlated with Microcystis,Desulfobacter,Chloracidobacter,Paenibacillus,and Peptococlostridium.