Much to the chagrin of germaphobes everywhere, our bodies are literally crawling with billions of bacteria both inside and out. Our digestive systems alone tend to contain roughly four pounds of bacteria and other microbes—and microscopic life also abounds on our skin, in our mouths, and on the surface of our eyes.
Though these concepts may make your skin crawl, it is also worth recognizing that many of these microbes play a key role in promoting health. Conditions running the gamut from poor digestion to chronic depression have all been explored for links to problems in the human microbiome—and some evidence suggests that many conditions might actually be improved by manipulating the microbial makeup of the microscopic ecosystems that exist in conjunction with our bodies.
Many of the aforementioned problems with the human microbiome tend to stem from a lack of microbial diversity. Naturally, humans are supposed to serve as life support systems for tens of thousands of distinct bacteria, viruses, and other microbes. Due to a variety of factors ranging from excessive sanitation to overuse of antibiotics, however, many of those microbial species end up losing significant percentages of their populations. Some of those species even go extinct within a given person: and once gone, some species of bacteria can be difficult to reintegrate.
This is all a bit concerning for NASA, and for anyone else who hopes to see continued human exploration of space. After all, if serious problems in the human microbiome are arising due to overuse of hand sanitizer, imagine what ongoing months spent in a near-sterile environment in outer space could do to astronauts!
Because of these potential issues, NASA has begun studying the impact that a sterile space station environment can have on its astronauts, and it has also begun researching the human ability to manipulate or artificially create microbiomes that would imitate an earthly experience. Such research is often referred to as MoEB, or the Microbiome of Built Environments.