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Space Changes Everything

By Rebecca McDonald|August 01, 2020

Improving space travel by studying the gut microbiome and more

Microgravity may exert tiny forces, but its relative impact can be significant. Humans and other earth-bound organisms have evolved with the constant pull of Earth’s gravity. As such, long-term exposure to a lack of gravity—or a minuscule amount known as microgravity—leads to problems like muscle loss and decreased bone density in astronauts. Additional potential problems, such as how microgravity affects human digestion, remain underexplored. This is in part because the digestive system is complex and works in tandem with billions of microorganisms that live in the gut, which are collectively known as the gut microbiome. To further investigate the effects of microgravity on this complex environment, the Defense Threat Reduction Agency funded a collaborative project between Los Alamos biologists Armand Dichosa and Anand Kumar and scientists at Rhodium Scientific, LLC. The team launched its first human gut microbiome experiment in March 2020 on the SpaceX-20 mission from NASA’s Kennedy Space Center.

Over decades of space travel, experiments have shown that many types of bacteria behave differently in space than on Earth. Some harmful bacteria, for example, can become more pathogenic, while others grow more slowly and are less pathogenic. This unpredictability has vexed the scientists tasked with keeping astronauts healthy. Some scientists theorize that the reason for this unusual behavior is because microgravity causes changes to the fluid environment in which the microbes live (e.g., saliva or stomach fluid). When the microbes don’t encounter “normal” fluid shear forces from their surroundings, they are not receiving the correct cues for their behavior. 

Astronauts enter space with a diverse population of bacteria in their gut microbiomes. Because they are only allowed to eat specific sterile food and drink sterilized recycled water—both of which lack the normal assortment of bacteria—astronauts have limited exposure to new bacteria while in space. This makes it easy for their microbiomes to develop an imbalance and can result in various disease conditions. On Earth, the gut microbiome has been shown to impact many aspects of human health, so understanding how microgravity might alter the microbiome is critical to protecting people operating in space.

The Los Alamos samples that were launched in March contained bacteria isolated from fecal donors with healthy gut flora. These bacterial flight samples were carefully prepared so that each culture would have a complementary sample remaining on Earth. Once they arrived at the International Space Station, the cultures were grown under specific conditions and preserved. Upon their return to Los Alamos, both sets of samples will be sequenced and analyzed to help the scientists identify any changes in the bacterial communities’ genomic signatures. 

“With this information, we may be able to prepare specific probiotics that could help astronauts remain healthy while they’re in space,” explains Kumar. 

A man taking gut microbe samples from a science freezer.
NASA astronaut and Expedition 62 Flight Engineer Andrew Morgan retrieves gut microbe samples from a science freezer for the Rhodium Space Microbiome experiment to understand how microgravity enriches or depletes the microbes that affect astronaut health. ISS

The impact of microgravity on human health has clear implications for long-term space travel. But the peculiar behavior induced by microgravity that has been observed so far inspires scientists to study more—from other living organisms to inanimate chemicals and materials. With a view towards expanding this type of research, the Los Alamos Center for Space and Earth Science (CSES) recently allocated special funding for projects that could lead to further studies on flights from the Spaceport America launch facility in southern New Mexico. The new research topics range from detecting urinary-tract infections to studying plant growth to exploring space-based manufacturing.

All together, these projects help pave the way for a deeper understanding of microgravity. This knowledge will not only improve the health and well-being of humans on long-term space visits; it could also help scientists harness the power of microgravity for a wide range of new applications valuable here on Earth.

Top image credit: STS-119 shuttle crew, NASA