Fig. 2

The gut microbiota of RA patients differs from that of controls. a Percentage of 16S reads of major phyla of the gut microbiota of RA patients and controls. b, c Rarefaction curves comparing the species richness (observed OTU numbers) (b) and the overall diversity (Shannon diversity index) (c) of RA patients and controls. The microbiota of RA patients exhibits significantly lower diversity. d–g Principal coordinate analysis plot based on the Bray–Curtis distance matrix constructed using OTUs from all phyla (d), Firmicutes (e), Bacteroidetes (f), and Actinobacteria (g). The percentage of variability explained by the corresponding coordinate is indicated on the axis. Each point represents a sample, red symbols indicate RA patients, and blue symbols indicate controls. The blue lines indicate vectors representing the relationships between the OTUs and each sample category. The ellipses serve a visual guide to group differences. PC principal component