Fig. 1

Different structures and diversity of the subgingival microbiota in the CN, aMCI, and AD groups. a The α-diversity indices Chao1, observed species, Shannon, Simpson, Faith’s PD, Pielou’s evenness, and Goods coverage. Statistical significance was set at P < 0.05. b Rarefaction curve of the Goods coverage index. With increasing sequencing depth, the Goods coverage index of the observed samples was close to saturation. c The structural shifts (β-diversity) presented by the Bray–Curtis PCoA plot based on the ASV abundance. The x-coordinate represents the first principal coordinate, the y-coordinate represents the second principal coordinate, and the percentage represents the influence rate of the principal coordinates on the sample differences. d Differences among the three groups. The statistical methods of c and d were both Adonis analysis. Data are presented as the mean ± SD. Statistical significance was set at P < 0.05. e The heatmap shows the comparisons of the subgingival microbial community in cognition-normal people and patients with AD and aMCI at the species level (top 100 species). The x-coordinate represents the names of the groups; the y-coordinate represents the taxon at the species level. f LEfSe analysis revealed significant bacterial differences in subgingival microbiota among the CN, aMCI, and AD groups. The LDA scores (log10) > 2 and P < 0.05 are listed