Community Structure And Diversity Analysis Of Aerobic Methanotrophic Bacteria In Biological Soil Crust Of Kubuqi Deserts

With global warming,the greenhouse effect and soil desertification have seriously hindered the sustainable development of global economy and society,which Have become two major problems of the global ecological environment.As a typical landscape of desert ecosystem,Biological soil crusts(BSCs)are widely distributed in arid and semi-arid environments all over the world.Methanotrophic in soil are the only known biogenic sink of atmospheric methane,which affects the net emission of methane from soil.However,in fact,the current research on methane oxidation flux of desert BSCs in China mainly focuses on coupling analysis of environmental factors,There is a lack of research on the diversity of community structure and function of Aerobic Methanotrophic bacteria in BSCs aggregates with different particle sizes.Two types of BSCs(cyanobacterial and moss crusts)were collected in the Kubuqi Sandy Land.By using the Illumina Novaseq sequencing platform for metagenomic sequencing,The diversity and community structure of Aerobic Methanotrophic bacteria in different aggregates of the two types crusts were compared and analyzed.At the same time,methane oxidation potential of BSCs was measured.Correlation analysis of soil physical and chemical properties of BSCS was conducted.The results are as follows:(1)Soil physical and chemical properties:the p H values of cyanobacteria crusts and moss crusts in Butaohai desert were slightly alkaline.Except for nitrate nitrogen(NO₃^--N),the contents of total nitrogen(TN),ammonium nitrogen(NH₄⁺-N),soluble organic carbon(DOC),total organic carbon(TOC),microbial biomass nitrogen(MBN)and microbial biomass carbon(MBC)of moss crusts were higher than those of cyanobacteria crusts.Among the aggregates,the overall nutritional level of BSCs with>0.25 mm was higher,that of<0.105 mm was the second,and that of 0.105-0.25 mm was worse than that of BSCs.(2)Abundance of Methanotrophic bacteria in BSCs:The abundance of Methanotrophic bacteria in mosss crust was higher than that in cyanobacteria crust.In both types of crusts,the abundance of Methanotrophic bacteria is the highest in L particle size aggregates,followed by the lowest in M particle size aggregates(3)Aerobiotic Methanotrophic diversity in BSCs:the sample Shannon index showed that the community structure diversity of methane oxidizing bacteria showed a trend of L>M>S in two types crusts,that is,the species diversity was the highest in>0.25 mm particle size aggregates and the lowest in<0.105 mm particle size aggregates,while the Chao1 index showed that there was no significant difference in Aerobiotic Methanotrophic richness in the samples.(4)BSCs aerobiotic Methanotrophic community structure:18 samples mainly included 2 phyla,namely Proteobacteria and Verrucomicrobia.Among them,Proteobacteria accounted for 98.17%,98.42%,and the relative abundance of,Verrucomicrobia was relatively low,only 1.58%,1.83%.There was no significant difference in the community structure of Aerobiotic Methanotrophic between cyanobacteria crusts and moss crusts at the gate level,but among different particle size aggregates,the relative abundance of Proteobacteria of>0.25 mm was higher than that of<0.25 mm.The dominant bacteria in cyanobacteria crusts are Methylocystis,Methylobacter and Methylosinus(the relative abundance is more than 10%).With the growth and development of BSCs,the dominant bacteria in moss crusts increased Methylomonas,compared with cyanobacteria crusts,and Methylocystis was the most dominant genus in both types of BSCs.(5)Correlation between microbial community and environmental factors:NH₄,MBN,MBC,TOC,TN and NO₃ had great influence on BSCs sample and its aerobiotic Methanotrophic community structure,while p H and AP had relatively little correlation with sample community structure.Moss crust samples were positively correlated with NH₄,AP,DOC,MBN,MBC,TOC and TN,while p H and NO₃ were negatively correlated with them.In cyanobacteria crusts,the aggregates of<0.25 mm particle diameter(M and S)were closely related to NH₄ and NO3,while the aggregates>0.25 mm(L)had relatively little correlation with environmental factors.(6)Methane oxidation ability analysis:the methane oxidation potential of moss crusts was significantly higher than that of cyanobacteria crusts,and the methane oxidation potential of BSCs was 2-3 times higher than that of cyanobacteria crusts.The methane oxidation potential of different particle sizes of CH₄,was M>L>S,and the CH₄oxidation ability of different samples tended to be flat after 72 hours of culture.