Research On Biogeography Of The Firmicuts And Bacteroidetes Communities In Xilin River Basin

Xilin River Basin across Typical Steppe region is a representative base for animal husbandry in China.As an important part of Eurasian grassland,this region has attracted intense scientific interest due to its influences on the global climate.Firmicutes and Bacteroidetes are the two dominant taxa of livestock intestinal microbiota in vivo.However,it has been still unclear that the environmental drivers and spatial distribution of Firmicutes and Bacteroidetes in vitro after livestock defecating into different soils.In the middle reach area of Xilin River Basin,we designated different functioning fields from the clean zone in river-bed center(RB),the livestock drinking zone in river-bed edge(RE),the livestock manure enrichment zone in oxbow lake(OL),the feeding zones in low-and high floodplain(LF and HF)and the enclosure zones of Typical Steppe in low-and high terrace(LT and HT).A total of 21 soil samples were from 3 alluvial soils in river-bed center(RB),6 boggy soils in river-bed edge(RE)and in oxbow lake(OL),3 swamp meadow soils in low floodplain(LF),3 meadow soils in high floodplain(HF),3 Leymus chinensis grassland soils in low terrace(LT),3 Stipa grandis grassland soils in high terrace(HT).16S r RNA gene high-throughput sequencing was employed to analyze the spatial distribution,diversity,compositions and abundance of the Firmicutes and Bacteroidetes communities in all samples.The physicochemical properties were used to explore the environmental drivers of spatial heterogeneity of Firmicutes and Bacteroidetes communities.The results were summarized as follows:(1)35 Firmicutes genera were dominated by the bacterial genera of classes Clostridia(77.14%),which reached the highest relative abundance in oxbow lake area rich in livestock manure(OL:9.47%).53 Bacteroidetes genera were dominated by the bacterial genera of classes Sphingobacteriia(43.40%)and Bacteroidia(18.87%),which reached the highest relative abundance in the clean zone in river-bed center(RB:31.29%).(2)The livestock manure enrichment zone in oxbow lake(OL)and the feeding zone in low floodplain(LF)had the highest diversity,dominated by Erysipelothrix,Tumebacillus,Acidaminobacter from Firmicutes phylum;uncultured Cytophagaceae and SB-5 members from Bacteroidetes phylum.The clean zone in river-bed center(RB)and the enclosure zone of Stipa grandis grassland in the high terrace(HT)had the lowest diversity,dominated by Chitinophagaceae members from Bacteroidetes phylum.(3)Soil water content itself and its combination with pH,TOC,NH₃-N,NO₃-N explained 54.7%and 59.1%of the spatial variability of Firmicutes and Bacteroidetes communities.In conclusion,Firmicutes and Bacteroidetes communities demonstrated obvious spatial heterogeneity in different functional fields associated with grazing activities from Xilin River Basin.Soil water content was possible factor directly or indirectly driving the spatial heterogeneity of the spatial variability of Firmicutes and Bacteroidetes communities.