Fig. 1

Bifidobacterium, particularly B. longum, was prevalent and dominant in the guts of subjects in a Chinese cohort, and the relative abundances of this genus and species were significantly associated with host age. A Triplot of a distance-based redundancy analysis (db-RDA) of the microbiota composition at the genus level relative to province, age, longevous district status, and sex. B Individual effect sizes of the gut microbiota covariates based on genus-level db-RDA and PERMANOVA analyses. C Comparisons of the Bifidobacterium relative abundance between age segments. The overall P value was calculated by Kruskal–Wallis test, while pairwise comparisons were conducted by Mann–Whitney U test. Significant differences (P < 0.05) between the age categories are indicated with different letters (a and b) above the bars. D Bifidobacterium species-level composition of the gut microbiota. Each column represents a sample. The stacked bars have been sorted according to the decreasing occurrence of B. longum. E Abundance of each bifidobacterial species relative to the total Bifidobacterium. Each dot represents a sample. F Triplot of a db-RDA of the microbiota composition at the Bifidobacterium species level relative to province, age, longevous district status, and sex. G Individual effect sizes of the gut microbiota covariates based on the Bifidobacterium species-level db-RDA and PERMANOVA analyses. H Comparisons of the B. longum relative abundance between age segments. The overall P value was calculated by Kruskal–Wallis test, while pairwise comparisons were conducted by Mann–Whitney U test. Significant differences (P < 0.05) between the age categories are indicated with different letters (a and b) above the bars. Among these analyzed phenotypes, the term “longevity/longevous district status” means whether a strain was isolated from the longevous districts or not. *P < 0.05, **P < 0.01, ***P < 0.001