Astronauts never travel alone in space. Every person traveling outside the world is accompanied by up to 100 trillion bacteria, viruses and other microorganisms, any number of which could endanger human health. Yet, we still don’t know how these communities of microscopic hitchhikers respond to microgravity. We don’t even know the full spectrum of space species living aboard the International Space Station (ISS). However, new studies are designed to change this. Last month, astronauts collected samples inside the ISS to build an unprecedented three-dimensional map of its microbiome. This spatial microbial census effort is the first step towards understanding, preventing and mitigating dangerous epidemics – whether they occur aboard the station, on long-term flights to Mars, or even back in hospitals.
We are constantly invaded by germs. From bacteria lining our guts to mites too small to see alive at the base of our eyelashes, it is estimated that there are at least as many microbes on and in us as there are human cells. “You can think of people as walking ecosystems,” says Pieter Dorrestein, a chemical biologist at the University of California, San Diego. Most of these tiny creatures are in fact essential and have such profound impacts on our health – affecting our immunity, our heart, and perhaps even our mental health – that scientists often refer to the microbiome as an “invisible organ”. In fact, there are so many microbial multitudes in us that their total mass can be roughly the weight of our brains.
Gallery: A glimpse of Mars from NASA’s Perseverance rover
So perhaps it’s no surprise that understanding the behavior of the microbiome during spaceflight is crucial if we are to send astronauts on long-term missions to Mars and beyond. But scientists aren’t just worried about the human microbiome, they’re also worried about the spacecraft’s microbiome. Take the example of the Russian Mir space station. In 1998, about three years before the station desorpted into the Pacific Ocean, scientists discovered several dozen species of bacteria, fungi and mites hiding behind a service sign. “I never imagined an inanimate object – a machine that works wonderfully like the station – as having a microbiome similar to someone who is alive, like a human,” says Serena M. Auñón-Chancellor, who is at both a doctor and a NASA astronaut. Yet, contrary to the notion of space as a sterile and inert environment, any spacecraft will inevitably harbor an assortment of microbes in sufficient numbers to crawl the skin of any astronaut.
The microbiome of a spaceship could prove to be dangerous for the health of astronauts. “Can you imagine that you take a long flight and all of a sudden you start catching, say, a carnivorous bacteria, and you can’t get rid of it?” Dorrestein said. “These are the kinds of consequences that could materialize.”
It is not a crazy idea. In 2006, a team of scientists sent a culture of salmonella bacteria for an 11-day ride on the space shuttle Atlantis to find that once the microbes returned to Earth, they more easily killed mice. Bacteria that have slipped off Earth’s surly bonds may also become more resistant to antibiotics – a recipe for disaster, given that long-duration space flights tend to weaken astronauts’ immune systems.
The new project launched by NASA’s Jet Propulsion Laboratory and UC San Diego could help mitigate the microbial threat. In February, astronaut Kate Rubins cleared 1,000 different locations on the ISS. This is about 100 times higher than the number of samples in typical microbial monitoring studies, which typically focus on the most suspicious parts of a living space such as kitchens, bathrooms and living areas. ‘exercise. The samples will be placed in a cold room and, in a few months, returned to Earth, where scientists will analyze their genetic signatures and name the different microbes to build a three-dimensional map of the entire ISS microbiome.
In addition, each swab will capture traces of molecules from food, oils, skin, etc. This prospect particularly excites Dorrestein, who is working on the project. Scientists currently know very little about the types of molecules on the ISS that fuel the growth of different microbial communities. The new map will help them connect specific molecules or nutrients to specific microbes. Through this link, scientists can develop guidelines to promote the growth of beneficial microbes and reduce harmful microbes – only through nutrients. It could be as simple as using specific building materials on a spacecraft to Mars. All of this suggests that the problem of a “sick spacecraft” may be partially resolved before it even reaches the launch pad.
But Kasthuri Venkateswaran, a microbiologist at the Jet Propulsion Laboratory and the project’s principal investigator, is very excited about the protective measures that could take place during transport. Although the current samples are sent back to Earth, he notes that astronauts will have to eliminate this intermediary on future missions. “When we go to other planets, you don’t have FedEx to return the samples,” says Venkateswaran. While scientists have the ability to perform genomic analysis aboard the ISS, the process is not particularly fast, and in the event of a dangerous outbreak, every moment can count (just think of the time that it often takes to get the results of a PCR test for COVID-19). “You want to make sure you can stay on top of this, because we’re all too aware these days of how a little bug can somehow mess up your world,” says David Klaus, space microbiologist at the University. from Colorado to Boulder.
To combat this problem, the Rubin swabs used in the station sweep test are double headed. One tip collects microbes for simple detection while the other intends to capture their metabolites – the natural chemical byproducts of microorganisms. Once Venkateswaran and his colleagues create a database linking specific microbes to certain metabolites, they can build small biosensors that only look for metabolites. Imagine a portable device that could diagnose the presence of bacteria or fungi on the spacecraft and immediately alert astronauts of an outbreak – similar to a carbon monoxide detector.
Notification of such a system (which Venkateswaran suspects it will take another five to ten years to become a reality) would trigger immediate action – as astronauts would step up their cleaning protocols to avoid an outbreak on board. “This will allow better maintenance of the habitat of tomorrow,” says Venkateswaran. Astronauts aboard the ISS are already working hard to keep the microbiome population under control. Every week, they vacuum the vents and wipe down surfaces with disinfectant wipes. Auñón-Chancellor estimates that while in orbit, each of the six astronauts on the crew spent about three hours a week cleaning. That is 18 hours per week for the total habitable volume of the ISS of only 388 cubic meters (about half of the passenger space of a Boeing 747), which may seem excessive. But given the unique circumstances of the ISS, all of this cleanup is necessary. “Up there, the food doesn’t fall on the floor,” she said. “The food goes to the ceiling. Food sticks to the walls. Food is everywhere. It is therefore a 3D cleaning. “
This kind of thorough cleaning has led some scientists to dismiss concerns about an epidemic en route to Mars. “I don’t think the influence of bacteria is really of much success for long-term spaceflight, because the evidence suggests otherwise,” Klaus says. “We have had people living on the [ISS] with teams in continuous rotation for over 20 years now. And there hasn’t been any kind of epidemic there. Auñón-Chancellor notes that just finding dangerous bacteria isn’t alarming – it’s only worrying if the microbes make astronauts sick. “I see it more as an identification and a warning,” she says. “And then we look and map and wait to see what these bacteria are doing in this stressful environment,” she adds.
But Venkateswaran is worried not only about the risks to astronauts, but also about the risks of microbial contamination from any otherworldly destinations they visit. “Astronauts are essentially a pathogen on the planet,” says Auñón-Chancellor. “It’s a new microbiome that suddenly took to Mars. Even the spacesuit they step out in will have the microbiome of their own mission on that suit’s material surface. If scientists could better map the microbiome to this combination, they could also clean it better. Venkateswaran hopes the research will even help scientists design premium suits with seals that prevent even the smallest microbes from escaping.
The unique apps don’t end there. For Liz Warren, senior program director at the US National Laboratory on the ISS, the most tantalizing aspect of all this research has little to do with space. Any partially enclosed environment – a house, an airplane, a hospital – will have its own microbiome. So, learning how to stop certain microbes from thriving in space (or stop them when they do) offers useful lessons for similar environments on Earth. For example, consider another ongoing ISS project that is testing the effectiveness of antimicrobial coatings manufactured by Boeing. The idea is that if the coatings work in space – where microbes can be much more dangerous – then they will work on Earth. In short, the ISS is an incredible laboratory in its own right. “You can’t do this on Earth – you can’t remove gravity from the image,” Klaus says. “Having microgravity is like having a microscope for the first time in a different way. You see behaviors that you might not otherwise see. “