**Figure 2.** **Comparison of the microbial composition between the young, adult and old groups.** (**A**) 3-D Principle component analysis (PCA) plot of samples along principle component (PC) 1,2 and 3, which explained 14.73%, 9.67% and 9.18% of the total variance, respectively. (**B**) Partial least squares discriminant analysis (PLS-DA) plot of gut microbiota among three groups: young (n=5, 2–4 years, green dots), adult (n=6, 5–13 years, red dots) and old (n=5, 17–20 years, blue dots).