Diversity And Environmental Driving Factors Of Methanotrophic Bacteria Community In Lake Wetland Sediments In Inner Mongolia

Methane(CH₄)is an important greenhouse gas second only to CO₂.Lakes and wetlands are one of the main sources of methane emission,accounting for 20-40%of the global methane emission sources.Methane-oxidizing bacteria in sediment aerobic layer play a key role in reducing methane emission from lakes and wetlands.The research shows that the methane-oxidizing bacteria in the environment are affected by many environmental factors such as salinity,p H,TOC,light intensity and so on.However,there are few studies on the community composition,diversity,activity and environmental driving factors of methane-oxidizing bacteria in lake wetland sediments in alpine areas on a large scale.Taking the sediments of 13 lakes and wetlands in the Inner Mongolia Plateau as the research object,based on the amplification sequencing of the methane oxidation monooxygenase coding gene pmoA,qPCR quantitative technology and the determination of methane oxidation potential,this paper studied the community structure composition,diversity,pmoA gene abundance and methane oxidation activity of methane-oxidizing bacteria in the sediments of lakes and wetlands,combined with the environmental factors of each habitat.The key factors affecting the distribution characteristics and activity of methane-oxidizing bacteria community were further analyzed.The analysis results are as follows:(1)The results of high-throughput sequencing and principal component analysis(PCA)based on pmoA gene showed that all samples were clustered into two clusters according to the salinity.Alphaproateobacteria is the main community composition of methane-oxidizing bacteria in the sediments of seven sample points with high salinity,which is dominated by type II methane-oxidizing bacteria,Methylosinus at the genus level(57.6%-76.3%).The other six samples with low salinity are mainly Gammaproteobacteria at the genus level,it is mainly type I methane-oxidizing bacteria Methylococcus(13.8%-57.5%).The results showed that salinity had a certain effect on the community composition of methane-oxidizing bacteria.(2)The results of redundancy analysis(RDA)showed that salinity had a greater impact on the community composition and diversity of methane-oxidizing bacteria than other environmental factors.Further pearson correlation analysis between the relative abundance of methane-oxidizing bacteria community composition and environmental factors showed that there are twevel bacterial generas significantly related to salinity,of which there is a very significant positive correlation with type II methane-oxidizing bacteria Methylosinus,while there was a significant negative correlation with other type I methane-oxidizing bacteria,which explained the reason why type II methane-oxidizing bacteria dominated rather than type I methane-oxidizing bacteria in high salinity sediments.(3)The results of co-occurrence network topology analysis show that there is a benign symbiotic relationship,not a competitive relationship,among which Methylobacter,Methylocystis,Methylococcus,Methylosinus,Methyloumidiphilus,Methylmicrobium,Methylotracoccus and other key methane-oxidizing microbial species play an important role in the composition of the whole methane-oxidizing bacterial community.(4)The results of pmoA gene abundance and methane-oxidizing bacteria activity showed that the copy number of pmoA gene in WSLZ sediment was the highest(2.36×10~7 copies/g dry weight),and there was significant difference in pmoA gene abundance between the sediments and other samples(P<0.05).The activity of methane-oxidizing bacteria(3.97?g·kg^-1·h^-1)in WLSH sediments was significantly higher than that in other samples.The results of linear regression analysis showed that salinity had a very significant negative correlation with the activity of methane-oxidizing bacteria(P<0.01),indicating that high salt environment would inhibit the activity of methane-oxidizing bacteria in sediments.By studying and analyzing the composition,diversity and activity of methane-oxidizing bacteria community in lake and wetland sediments in Inner Mongolia,the environmental driving factors affecting the composition and diversity of methane-oxidizing bacteria community were explored,which filled the gap for the large-scale research of methane-oxidizing bacteria in lake and wetland in Inner Mongolia Plateau.