Comparative analyses of fecal microbiota in Tibetan and Chinese Han living at low or high altitude by barcoded 454 pyrosequencing

Abstract

Knowledge about the impact of altitude and ethnicity on human gut microbiota is currently limited. In this study, fecal microbiota from 12 Tibetans (T group), 11 Chinese Han living in Tibet (HH group) and 12 Chinese Han living in Shaanxi province (LH group) were profiled by 454 pyrosequencing. Analysis of UniFrac principal coordinates showed significant structural changes in fecal microbiota among the three groups. There were significant differences in the composition of fecal microbiota among the three groups at phylum and genus levels. At the phylum level, the fecal samples of HH and T groups had higher relative abundances of Firmicutes, whereas the LH group had a higher relative abundance of Bacteroidetes. These changes at the phylum level reflected different dominant genus compositions. Compared with the LH group, changes of Firmicutes and Bacteroidetes were mainly due to a significant decrease of Prevotella in the HH group and were primarily attributable to significant decreases of Bacteroides and Prevotella as well as a significant increase of Catenibacterium in the T group. In conclusion, our results suggest that high altitude may contribute to shaping human gut microbiota. Genetic and dietary factors may also explain the different microbiota compositions between Tibetan and Chinese Han.

Figure 1. Rarefaction curves and Shannon-Wiener curves of each sample.

Shannon-Wiener curves (A) and rarefaction curves (B) were all calculated at the 97% similarity level with pyrosequencing data in microbiota from groups of LH, HH and T. LH = Chinese Han living in Shaanxi; HH = Chinese Han living in Tibet; T = Tibetans.

Figure 2. Relative abundance of bacterial phyla (A) and classes (B) in fecal microbiota of three groups.

LH = Chinese Han living at the lowland; HH = Chinese Han living in Tibet; T = Tibetans.

Figure 3. Heatmap of the distribution of the relative abundance of the genera.

(A) Taxonomic classification of the genera. (B) Genera detected and statistical analysis among three groups (Metastats for the sequence count data). LH = Chinese Han living in Shaanxi; HH = Chinese Han living in Tibet; T = Tibetans. Significance: NS > 0.05, *≤0.05; **≤0.01.

Figure 4. Weighted UniFrac principal coordinates analysis (PCoA) plots based on weighted UniFrac metric.

LH = Chinese Han living in Shaanxi (green dots); HH = Chinese Han living in Tibet (red dots); T = Tibetans (blue dots).

Figure 5. Canonical analysis of principal coordinates (CAP) of human gut microbiota with different ethnicity and altitude.

CAP1 was the ethnic axis and CAP2 was the altitude axis. ANOVA test showed significant influence of the two constraints (p = 0.001). LH = Chinese Han living in Shaanxi; HH = Chinese Han living in Tibet; T = Tibetans.

Figure 6. Relative abundance of total bacteria per 10 ng DNA (A), ratios of Firmicutes:total bacteria (B), ratios of Bacteroides:total bacteria (C), and ratios of Firmicutes:Bacteroides (D) in the fecal samples of three groups.^a,b

Different lower-case letters indicate significant differences between groups. LH = Chinese Han living in Shaanxi; HH = Chinese Han living in Tibet; T = Tibetans.