Dirtying the International Space Station (ISS) to live there in better health? A strange idea proposed by a team of American researchers. Their study, published In Cell Press, shows that the ISS has a significantly lower microbial diversity than terrestrial environments. According to them, the closed and aseptic environment could be at the origin of many of the health problems encountered by astronauts during their space travels, from immune dysfunctions to skin rashes and other inflammatory problems.
Read alsoTwo American astronauts stuck on the ISS could return home a little earlier than expected
A spatial distribution of microbes
To study the microbial environment on the ISS, the researchers collaborated with astronauts, who collected 803 samples from different surfaces, about 100 times more samples than in previous studies. Once the samples returned to Earth, the bacterial species and chemicals present on the ISS could be analyzed.
The researchers created three-dimensional maps showing the location of each sample on the ISS. They found that their distribution followed the layout of the station's different modules (rooms). For example, dining and food preparation areas had more microbes associated with food, while space toilets had more microbes and metabolites associated with urine and feces.
This seems logical. The distribution of microbes linked to human actions is not so different on Earth, but they are more numerous and above all, more diverse!
Human skin is the main source of microbes in the ISS samples, followed by the mouth and nose. On Earth, however, the environment contains a multitude of microorganisms living in the soil, water or air. In space, astronauts tend to be surrounded by their own microbes, and develop diseases.
Read alsoHydrogel suits to protect astronauts from cosmic radiation
Dirty to heal better
To combat these microbes, astronauts use cleaning products in large quantities. Traces of these chemicals were omnipresent in the samples brought back from the ISS. According to the researchers, these samples are comparable to those from hospitals. In these sterile environments, human microbes could more easily develop resistance to the products.
"There's a big difference between being exposed to healthy soil through gardening and wallowing in your own filth, which is kind of what happens if we're in a strictly enclosed environment without a continuous supply of these healthy sources of microbes from outside.", said Rob Knight, a researcher at the University of San Diego and co-author of the study, in a statement.
According to the researchers, intentionally integrating these microbes and the substrates they live in into the ISS could improve astronauts' health without sacrificing hygiene. The benefits could be similar to those of a good gardening session on the immune system! “ If we really want life to develop outside of Earth, we must start to think about what other beneficial companions we should send with these astronauts to help them develop sustainable ecosystems,” explains Rodolfo Salido, co-author of the study.
By refining their analyses, the researchers hope to find potentially pathogenic microbes on the ISS, and thus help improve the health of people who live and work in similar sterile environments on Earth.
English 
French