Response of human gut microbiota under simulated microgravity.

The present study was conducted to investigate the influence of microgravity on human gut microbiota using 16S rRNA gene sequencing in vitro. The diamagnetic material magnetic levitation method was used to simulate weightless environment. The human gut microbiota was cultured under two different conditions: normal gravity (1 g), and simulated microgravity (0 g), which showed that both the richness (P = 0.04) and diversity (P = 0.0002) of human gut microbiota were significantly altered. As compared to the normal gravity, the simulated microgravity significantly reduced abundance of bacteria related to anti-inflammatory effects, such as Subdoligranulum, Faecalibacterium, Fusicatenibacter, Butyricicoccus, and Lachnospiraceae-NK4A136-0 group (P < 0.05), while significantly increased that of Alistipes and Eubacterium-Ventriosum-group (P < 0.05). Moreover, the Spearman's correlation analysis showed that there were more significantly correlated species (|r|≥ 0.5, P < 0.05) in normal gravity than that in the simulated microgravity. KEGG pathway analysis revealed that the microgravity significantly (P < 0.05) affected the metabolism of gut microbiota, such as the metabolism of pyrimidine, fatty acids, glyoxylate and dicarboxylate, peptidoglycan biosynthesis, and carbon fixation in photosynthetic organisms. These results suggested that the exposure to a microgravity environment might induce disturbances in human gut microbiota. KEY POINTS: • Using 16sRNA gene sequencing technology, it was found that magnetic levitation-simulated microgravity had varying degrees of influence on the abundance, diversity, species correlation, and KEGG pathways of human intestinal microbes. • Digital PCR can improve the detection rate of microorganisms with low abundance.