The effects of combined environmental factors on the intestinal flora of mice based on ground simulation experiments

Abstract

The composition and function of intestinal microbial communities are important for human health. However, these intestinal floras are sensitive to changes in the environment. Adverse changes to intestinal flora can affect the health of astronauts, resulting in difficulties in implementing space missions. We randomly divided mice into three groups and placed each group in either a normal environment, simulated microgravity environment or a combined effects environment, which included simulated microgravity, low pressure and noise. Fecal samples of the mice were collected for follow-up analysis based on metagenomics technology. With the influence of different space environmental factors, the species composition at the phylum and genus levels were significantly affected by the combined effects environment, especially the abundance of the Firmicutes and Bacteroidetes. Furthermore, screening was conducted to identify biomarkers that could be regarded as environmental markers. And there have also been some noticeable changes in the function of intestinal floras. Moreover, the abundance of antibiotic resistance genes (ARGs) was also found to be changed under different environmental conditions, such as bacitracin and vancomycin. The combined effects environment could significantly affect the species composition, function, and the expression of ARGs of intestinal flora of mice which may provide a theoretical basis for space medical supervision and healthcare.

Figure 1

The workflow diagram of the present study.

Figure 2

The results of the prediction of genes and their relationships. (a) The number of genes in the three groups is shown in the violin plot. (b) The intersection of the predicted genes among the three groups.

Figure 3

The overall results of species annotation and the correlation analysis of all samples. (a) Merged species information of all three groups based on GraPhlAn. (b,c) The PCA and NMDS analysis of all samples. (d–f) d, e, and f represent the species annotation of the NC, TS, and TS + SM groups, respectively.

Figure 4

The relative abundances of species and heat maps of all samples. (a,b) The relative species abundance at phylum level and genus level. (c,d) The heat map of species abundance at phylum level and genus level.

Figure 5

The results of the screening of biomarkers from all three groups. (a) The LEfSe score of the biomarkers in the three groups. (b) The cladogram of representative biomarkers and their evolutionary relationship. Note The Biomarkers with no significant difference were uniformly colored yellow. The different color nodes represented the microbial groups that played an important role in the three groups.

Figure 6

Functional enrichment analysis of all samples. (a,b) The results of the functional enrichment analysis of all samples using the KEGG and eggNOG databases. (c,d) The heat map showing the enriched functions of all samples obtained using the KEGG and eggNOG databases.

Figure 7

The predicted ARGs and their relative abundance in all samples. (a) The number of ARGs identified in the three groups. (b) The relative abundances of the top 15 ARGs in all samples. (c) The cluster heat map of the ARGs in all samples.