The 16S rRNA sequencing analysis
All samples were sequenced to produce 1,267,914 effective sequences and 1,222,131 high quality sequences were generated after optimization. A total of 69,222 OTUs were obtained by classifying all sequences with 97% similarity. Among the sequences, there were 21 at the phylum, 37 at the class, 71 at the order, 138 at the family, and 297 at the genus levels. Each sample contained an average of 35,945 high-quality sequences and 2036 OTUs. The dilution curves for Goods Coverage (Figure. 2) and Observed Species (Figure. 3) were drawn. All the sequenced samples reached the platform stage, thus indicating that the sequencing quantity and depth were adequate to cover most of the bacteria.