Abstract
In the last few decades there has been a surge in interest in space travel, not just from government-backed research institutions like NASA, but also from private business owners looking to expand their ventures into commercial space flight. However, this brings up the concern of radiation exposure outside the confines of the atmosphere and what risks it may pose to our gut microbiota and, by association, our health. Previous studies with mouse models have shown that exposure to space-type radiation causes decreased diversity and relative abundance of beneficial taxa (as well as increased abundance of pathogenic taxa) but did not explore the temporal dynamics of these changes. Our study investigates the temporal changes in the gut microbiome after radiation exposure to determine what dose presents the limit to unaided recovery, what specific taxa maintain the strongest foothold soon after exposure, and what key metabolic functions are lost or gained. We utilized a NASA-collected 16S rRNA dataset, obtained from radiation-exposed mice at 10 days and 30 days post-treatment and compared diversity metrics, differentially abundant taxa, and metabolic functional potential between the two timepoints. We found that unaided recovery of alpha diversity to pre-exposure levels was only observed up to a dose 0.1 Gy, while beta diversity displayed a nonlinear response to absorbed radiation dose. Unusually, core microbiome analysis revealed that 0.1 Gy and 1 Gy had the most similarities in genera. At 0.1 Gy, the Lachnoclostridium and Lachnospiraceae FCS020 were able to recover from 10 to 30 days, while at 1 Gy, Bifidobacterium, Clostridium sensu stricto 1, and Dubosiella exhibited decreased relative abundance from 10 to 30 days. At 0.1 Gy, pathways related to purine degradation were found to have increased abundance at 30 days. In contrast, we observed widespread decreases across many metabolic pathways at 1 Gy, suggesting a broader disruption of microbial metabolism over adaptive response. The observed dose dependent changes in differential abundance of important taxa, coupled to dose dependent functional shifts identify potential target taxa for medical restoration post radiation exposure and metabolites and vitamins for supplement development.