Variations in Urinary Microbiota on a Short-Duration Space Mission to the International Space Station

Space travel exposes crew to substantial stressors, which may potentially alter their microbiome and be detrimental to their health and safety. We hypothesize that urinary microbiota is altered during a short-duration spaceflight to the International Space Station (ISS).

Urine samples were collected from 4 male crew members. One crew member provided samples while on orbit on the ISS using a urine collection kit (UCK) designed for low-gravity environments. This crew member also provided paired mid-stream and UCK samples on Earth prelaunch and on return for direct comparison of collection methods. Three additional crew members provided mid-stream samples prelaunch and on return, and also for follow-up timepoints to serve as ex post facto control samples. Urine was stored at -80℃ and sent for 16s next-generation sequencing (MicroGenDX, Lubbock, TX).

Bacterial load (P = .52), species richness (P = .64), and differences in microbiota composition (P = .26) did not significantly vary by the collection method (mid-stream vs UCK). Significant differences in species richness, load, and microbial composition among preflight, orbital, and return mission samples were detected (P = .047, F = 1.8092, df = 2.9, R2 = 0.34076). Orbital microbial composition significantly differed from preflight (P = .03) and return (P = .03), whereas preflight and return samples did not differ (P > .05). Comparison with the limited follow-up ex post facto Earth-bound samples serving as controls showed no significant differences among preflight or return mission samples, but preflight (P = .04) and return (P = .05) did significantly differ compositionally from orbital samples. Continuous temporal effects on composition were evaluated through which bacterial load (P = .05) was statistically significant, peaking during the orbital period.

Results are consistent with an effect of space travel altering the urinary microbiota. Further studies are needed to confirm this result and to better understand whether such changes may be detrimental to the health and safety of space travelers and professional astronauts.