(a) The sequence composition of samples at each taxonomic level. Sequence number percent indicates the ratio of the number of sequences annotated to this level to the total annotation data. (b) Annotation results of grouping relative abundance (species). Relative abundance is the ratio of the number of bacteria that are annotated to species to the total number of bacteria. (c) Species abundance cluster. (d) Heatmap of beta diversity index. The number in the square is the coefficient of dissimilarity between two pairs of samples. The smaller the coefficient of difference is, the smaller the difference of species diversity is. In the same box, the values of upper, middle, and lower represent weighted UniFrac, unweighted UniFrac, and Bray–Curtis distance.