Space & Innovation

The ISS Bacterial Community Resembles What You'd Find in Your Home

Despite the space environment being very controlled, with only a handful of astronauts visiting each year, the microbes aboard appear to be robust.

Microbes naturally exist no matter where humans reside. And it turns out that the microbes on board the International Space Station look more like what you’d find in your living room than what you would find on a human body.

That’s the result of a new study of swabs taken by astronauts on the orbiting complex. The results were published in PeerJ, a peer-reviewed open access journal.

"‘Is it gross?’ and ‘Will you see microbes from space?’ are probably the two most common questions we get about this work," said co-author David Coil, a microbiologist at the University of California, Davis, in a statement. "As to the first, we are completely surrounded by mostly harmless microbes on Earth, and we see a broadly similar microbial community on the ISS. So it is probably no more or less gross than your living room."

The astronauts took their samples from 15 locations on the ISS. Despite its remote location, thousands of species live on the space station. But what’s more interesting is the variety of bacteria that are found. The researchers compared the space bacteria to those found in homes (from a study called "Wildlife of Our Homes") and human bodies (the Human Microbiome Project).

They found that the types of bacteria are similar to what you would find in a typical home. That’s interesting because the space environment is very controlled; only a handful of astronauts visit a year. The only other influx of microbes happens when astronauts unload a visiting spaceship, such as a SpaceX Dragon. Despite this, the community of microbes living alongside the astronauts appears robust.

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"The microbiome on the surfaces on the ISS looks very much like the surfaces of its inhabitants, which is not surprising, given that they are the primary source," said Jennifer Lang, lead author of the study and a former postdoctoral researcher at UC Davis. "We were also pleased to see that the diversity was fairly high, indicating that it did not look like a ‘sick’ microbial community."

Project MERCCURI swabs being retrieved after splashdown in February 2015. | Carl Carruthers

While it’s interesting to find out which microscopic critters live among astronauts, this the research carries implications for Earth microbes as well. For example, researchers can do comparative studies with buildings on Earth, using the ISS as a sort of control because microbes only arrive in limited quantities.

This isn’t the first time this team has tackled bacteria in space. The researchers use the moniker Project MERCCURI, which stands for Microbial Ecology Research Combining Citizen and University Researchers on ISS. (MERCCURI’s moniker is an apparent riff on NASA’s Project Mercury, the first NASA human spaceflight program, which ran missions between 1961 and 1963.)

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A 2015 MERCCURI paper described how the microbial researchers isolated a newly found type of bacteria, called Porphyrobacter mercurialis, from a stadium seat. Then they rocketed it off to the ISS to see how it would do in space. In 2016, the researchers did a sort of microbial Olympics, tracking how well 48 bacteria (collected across the United States) grew on the station.

One microbe from that study appeared to grow better in space — Bacillus safensis JPL-MERTA-8-2. That strain was first found in a spacecraft clean room before the launch of the two Mars Exploration Rovers (Spirit and Opportunity) in 2004.

In unrelated claims, Russian cosmonauts recently claimed to found bacteria outside of the station – something that NASA generally has little comment about, given that this is work from Roscosmos and not the US space agency.

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Just a few days ago, cosmonaut Anton Shkaplerov told TASS (a Russian state-owned news agency) that spacewalking Russians collected bacteria from the exterior of the ISS that weren’t there during the launch of the module. While some news reports quickly said these bacteria must be extraterrestrial, other outlets such as CNET said it most likely arises from human contamination of some sort.

This follows a 2014 assertion by Russian space official Vladimir Solovyev, who made unconfirmed claims (also reported in TASS) that astronauts found sea plankton outside of the ISS.

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