Every time astronauts voyage to and from the International Space Station (ISS), they bring trillions of microbial hitchhikers along with them. Humans are buckets of bugs, after all, and as ISS progenitors like the Mir space station have aptly demonstrated, our live-in companions will colonize our surroundings whether we are off Earth or on it.
With that in mind, gaining a firmer understanding of how common microbes adapt to life in space is essential to anticipating some of the challenges of long duration human spaceflight.
Enter: Project MERCURRI (Microbial Ecology Research Combining Citizen and University Researchers on ISS), an enormous interdisciplinary collaboration between scientists, activists, and thousands of volunteer participants.
A few years back, the Project MERCURRI team crowdsourced microbial samples from a wide range of surfaces, including the Liberty Bell, Sue the T. rex, and Al Roker’s studio weather wall. Samples from shoes and cell phones were also collected from volunteers at sports events across the country.
Darlene Cavalier swabs the Liberty Bell. Image: NASA/Project MERCURRI
From there, the impressive collection was narrowed down to 48 non-pathogenic bacterial candidates that were launched to the ISS on April 19, 2014. The results of this long term experiment are published today in the open access journal PeerJ.
“Part of our hope here was to inspire people to think more about the non-pathogenic microbes that surround us, but also about research on the space station,” said lead author David Coil, a UC Davis microbiologist and Project MERCURRI co-investigator, in a phone interview with Motherboard.
“A lot of the people that we engaged on this project had basically never thought about either the space station or microbiology because we grabbed people at sporting events. We really engaged a lot of people who became quite interested in the whole thing that weren’t otherwise likely to think about it.”
In addition to fostering a sense of public engagement and citizen science, the experiment set itself apart as one of the only investigations into non-pathogenic bacteria on the ISS. Understandably, it is more common to research pathogens—microbes that can cause infections or disease—because those lifeforms pose a greater threat to astronauts on long duration missions, like crewed Mars missions.
But as Coil and his co-authors point out, non-pathogens can influence the behavior and propagation of pathogens in the immune system, so it’s important to study the dynamics of the entire microbiome of space environments in order to mitigate health risks.
Sample of unclassified Spingomonadaceae from a stadium seat in Niedermeyer Field collected by the Pop Warner Coronado cheerleaders, San Diego, CA. Image: Alex Alexeiv/UC Davis
“Say you sterilize a hospital room completely, then you run six people through it,” Coil said. “You have created all these niches and spaces for pathogens to hang out in without the normal defense of a healthy microbiome.”
“It’s definitely speculative to apply that to something like spaceflight,” he cautioned, “but it’s not unreasonable to hypothesize that it’s probably a good thing to have a healthy ecosystem of non-pathogenic microbes surrounding and in people in a spacecraft as well.”
The good news is that Coil and his colleagues discovered that most of the microbes didn’t seem to be thrown off by life in space at all. “We sent up a collection of bugs and most of them pretty much did the same things that they do on Earth,” Coil said. “I find that sort of conceptually reassuring.”
The exception was a strain called Bacillus safensis JPL-MERTA-8-2, a specimen that was swabbed off of one of the Mars Exploration Rovers before they launched in 2004, and may have accompanied those spacecraft to Mars. According to the new study, B. safensis grew an astonishing 60 percent better in space than its counterpart on Earth, for reasons that are not yet clear.
“For an individual bacterium, I don’t think gravity probably makes any difference,” Coil said. “Bugs are pretty small, so gravity is not a major determining factor on their day-to-day metabolism and physiology.”
“At the level of a community of bacteria, however, gravity looks like it does have some influence,” he continued. “My guess is that something like that is going on here, where for this bug [B. safensis], there’s something about less gravity that is favorable to its growth as a community. But to really get at it, you’d want to send that bug back up there under some different conditions and maybe have [the ISS crew] do some more in-depth experiments.”
But that is a project for another time, and perhaps, another team. “We have lots of other ideas for other citizen science projects moving forward, but none of which involve space,” Coil said, “mostly because space is actually a giant pain in the ass. The logistical and bureaucratic hurdles associated with doing work in space are astounding. It’s really cool to do something like this, but it’s a huge hassle compared to just growing stuff up in the lab.”
Instead of becoming enmeshed in space-related red tape again, the Project MERCURRI team intends to generate data points from the 3,000+ samples collected from around the country, to root out overarching microbial patterns here on Earth.
Meanwhile, the lush microbiome of the ISS will continue to flourish as crews come and go, whether it is under scrutiny or not. Perhaps one day, these intricate ecosystems will accompany their human hosts to distant worlds and alien habitats, but for now, it’s enough to observe their fascinating reaction to spaceflight from our own orbital backyard.