Novel condition in spaceflight and specialized food bar caused atypical gut microbial composition

Spaceflight presents an ensemble of stress factors encompassing chronic unloading, microgravity, low-grade irradiation, disrupted circadian rhythm and novel environment. Its consequences are multidimensional causing energy deprivation, immune suppression, osteoporosis and delayed healing. Emerging knowledge showed that the gut microbiota plays crucial roles in regulating many of hosts health determinants, such as metabolism, energy biosynthesis, neurological and immunological functions. Potentially, spaceflight induced stress can act as a major selective power to alter the gut microbial ecosystem. To address this tenet, we undertook a deep metagenomics sequencing of descending colon contents from C57BL6j male mice flown under the NASA Rodent Research 4 program. Before launch, a subset of this cohort was operated to create a segmental bone defect in their femurs, and this cohort was used to interrogate a wound healing model in space. Healthy sham and SBD mice were housed at ISS for one month in parallel to their ground controls before being humanely euthanized. Spaceflight induced stress emerged as the more dominating factor than SBD in shifting the diversity profile in bacteria and eukaryotes in DCC, while the cumulative impacts of spaceflight and SBD emerged as the major contributor of viral diversity. Spaceflown DCC had less abundant bacterial phylum named Bacilliota than the ground samples, which was compensated by increased colonization of Bacteroidota and Verrucomicrobiota in spaceflight. Individual taxonomic inspection revealed a few taxa of atypical abundances. Staphylococcus nepalensis that typically found in high altitude on ground was highly colonized in spaceflight, Listeriaceae, a radiation-sensitive bacterial family was depleted in spaceflight, furthermore, multiple taxa across the kingdoms that are related to intestinal homeostasis and overall gut health emerged perturbed in spaceflight. Proteomics assay of intestinal epithelia suggested its compromised mucosal barrier. In conclusion, current findings highlighted the imposing selection power of spaceflight to modulate the microbial ecosystem that calls for customized therapeutic and dietary strategy for astronauts.