"Future built environments, including space stations, could benefit from intentionally fostering diverse microbial communities that better mimic the natural microbial exposures experienced on Earth, rather than relying on highly sanitized spaces," explained Rodolfo Salido, co-first author from the University of California, San Diego (UC San Diego).

The study involved collaboration with astronauts who collected 803 surface samples across the ISS-far exceeding the scope of previous surveys. Upon returning to Earth, researchers analyzed the bacterial species and chemicals present in each sample. The findings were used to create detailed three-dimensional maps highlighting the distribution of microbes and chemicals throughout the ISS.

Results indicate that human skin is the predominant source of microbes in the station. Additionally, disinfectants and cleaning chemicals were found extensively across surfaces. The study also found that different sections of the ISS contained distinct microbial and chemical compositions based on their usage. For instance, food-associated microbes were more prevalent in dining areas, while restroom spaces exhibited higher concentrations of urine- and fecal-associated microbes and metabolites.

"We noticed that the abundance of disinfectant on the surface of the International Space Station is highly correlated with the microbiome diversity at different locations on the space station," said co-first author Nina Zhao (@NinaHaoqiZhao) of UC San Diego.

When comparing ISS samples to microbial environments on Earth, researchers discovered that the station's microbial communities were less diverse than most Earth-based samples. The ISS microbiome resembled that of sterile, industrialized settings such as hospitals, closed habitats, and urban homes, while lacking microbes typically found in soil and water. The team suggests that incorporating beneficial environmental microbes into the ISS could enhance astronaut health while maintaining hygiene standards. They liken this to the well-documented immune benefits of gardening.

"There's a big difference between exposure to healthy soil from gardening versus stewing in our own filth, which is kind of what happens if we're in a strictly enclosed environment with no ongoing input of those healthy sources of microbes from the outside," said researcher Rob Knight.

Moving forward, scientists aim to refine their techniques to identify potential pathogens and assess how environmental metabolites might signal astronaut health. These methods could also be applied to improve conditions in similarly sterile environments on Earth.

"If we really want life to thrive outside Earth, we can't just take a small branch of the tree of life and launch it into space and hope that it will work out," Salido emphasized. "We need to start thinking about what other beneficial companions we should be sending with these astronauts to help them develop ecosystems that will be sustainable and beneficial for all."

Research Report:The International Space Station Has a Unique and Extreme Microbial and Chemical Environment Driven by Use Patterns

Related Links
University of California San Diego
Space Medicine Technology and Systems