Community Structure And Diversity Of Aerobic Anoxygenic Phototrophic Bacteria In Biological Soil Crusts’ Different Size Aggregates Of Kubuqi Deserts

Biological Soil Crusts(BSCs)widely arise in places whose weather is arid and semi-arid around the world.As a significant element to improve the desert ecosystem,the BSCs have multiple functions,such as reinforcing the environmental stability,and expediting the process of environmental recovery and rebuilding.Soil aggregation is a vital part of the process in which the soil plays its role,and is a crucial indicator to show the quality of the soil.The mode of form soil aggregation is usually utilizing the physical and chemical path,and the process of the soil aggregation form relates to BSCs’development.Aerobic anoxygenic phototrophic bacteria(AAPB)play a crucial role in BSCs’formation and development and maybe play a vital role in soil aggregation formation and stabilization.There is rarely reported on the community structure and diversity of the AAPB in different soil aggregations.In this research,BSCs collected from the eastern part of the Kubuqi desert.Using the high-throughput sequencing platform-Miseq to contrast the cyanobacterial crusts and moss crusts’the diversity and community structure of AAPB at different soil aggregation combined with the correlation analysis of soil chemistry and soil enzyme activity.The follows are the results:(1)The soil enzyme activity was manifested as higher in the large particles aggregatesExcept for leucine aminopeptidase(LAP),the activity ofβ-1,4-glucosidase(BG),cellobiohydrolase(CBH),Urease(UR),andβ-1,4-N-acetylaminoglucosidase(NAG)of cyanobacterial crusts were higher than the counterpart of moss crusts.In the same crusts,the soil enzyme activity of>0.25 mm soil aggregation was higher than the counterpart of<0.25mm(including 0.25-0.105 mm,<0.105 mm).The>0.25 mm of moss crusts has the maximum value.(2)The abundance of AAPB was manifested as higher in the large particles aggregatesThe abundance of AAPB in moss crusts was higher than in cyanobacterial crusts.The maximum value has appeared in>0.25 mm of cyanobacterial crusts(4.50×10~6copies/g·soil),and the minimum value has appeared in 0.25-0.105 mm of moss crusts(4.06×10~5copies/g·soil).In the same type of crusts,the abundance of AAPB is the highest in>0.25 mm,followed by 0.25-0.105 mm,and the lowest in<0.105 mm size aggregates.Shannon and Chao1 indexes had no significant difference in different samples,showing no change in cyanobacterial crusts and moss crusts or different aggregates.(3)The community structure of AAPB and the key environmental factors which influence its,in BSCsThe AAPB mainly belongs to 3 phylums namely:Proteobacteria(57.20-72.93%),Chloroflexi(7.24-35.09%)and unclassified＿d＿＿Bacteria(7.12-19.30%),and the Proteobacteria accounted more than 50%;The AAPB mainly belongs to 5 classes namely:Alphaproteobacteria(56.45-70.13%),Chloroflexia(7.22-35.09%),unclassified＿d＿＿Bacteria(7.12-19.30%),Gammaproteobacteria(0.47-2.13%)and Betaproteobacteria(0.28-0.78%).The families which accounted for more than 10%:Roseiflexaceae(7.21-35.08%),Methylobacteriaceae(9.31-25.30%),unclassified＿d＿＿Bacteria(7.12-19.30%),Bradyrhizobiaceae(6.38-17.85%)and Acetobacteraceae(8.38-20.27%).The genuses which accounted for more than 10%:Roseiflexus(7.21-35.08%),Methylobacterium(9.31-25.30%),unclassified＿d＿＿Bacteria(7.12-19.30%),Bradyrhizobium(6.07-17.14%)and Rubritepida(5.80-19.31%).Unclassified＿d＿＿Bacteria,unclassified＿d＿＿Bacteria,Gammaproteobacteria,Methylobacteriaceae,unclassified＿d＿＿Bacteria,Bradyrhizobiaceae,Sphingomonadaceae,unclassified＿c＿＿Gammaproteobacteria,Methylobacterium,unclassified＿d＿＿Bacteria,Bradyrhizobium and Sphingomonas has significant difference in different samples.The key environmental factors which influence the community structure of AAPB in different BSCs and aggregates were nitrate nitrogen and ammonium nitrogen.And the critical soil enzymes which influence the community structure of AAPB in different BSCs and aggregates wereβ-1,4-glucosidase(BG),β-1,4-N-acetylaminoglucosidase(NAG),and leucine aminopeptidase(LAP).In conclusion,with the development of BSCs and the change of aggregate,the community structure of AAPB in BSCs has a significant difference.The key factors which influence the community structure of AAPB were nitrate nitrogen,ammonium nitrogen,β-1,4-glucosidase(BG),β-1,4-N-acetylaminoglucosidase(NAG)and leucine aminopeptidase(LAP).