NASA Clean Rooms Loaded with Microbial Stowaways
A researcher gets on their hands and knees of a spacecraft assembly floor to sample extreme microbes.
Credit: NASA/Jet Propulsion Laboratory/California Institute of Technology

NASA builds its spacecraft in some of the tidiest rooms on Earth, but a few microbial stowaways always manage to survive and sneak a ride into space.

That could be because the space agency's super-sterile "clean rooms" nonetheless support a greater variety of microbes than previously thought, researchers have now found. And, there more of them than expected. NASA is cataloging the potential hitchhikers as a result, so they can be easily sorted from potential extraterrestrial life that might one day be detected somewhere in the solar system.

?These findings will advance the search for life on Mars and other worlds,? said study co-author Kasthuri Venkateswaran, a microbiologist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

Venkateswaran and his group's findings are detailed in a recent issue of the journal FEMS Microbiology Ecology.

Some like it clean

Most bacteria prefer plenty of food and fresh air, but some love "extreme" environments and thrive on just the paint and leftover cleaning solvents found in some NASA clean rooms. Some of the rooms, in which the air is continuously filtered, harbor fewer than 10 particles per cubic foot (0.03 cubic meter)--that's about 100,000 fewer dust particles than an equal cube of outdoor air.

Catharine Conley, an astrobiologist and planetary protection officer at NASA headquarters in Washington, D.C., said a lack of competition may cause the super-clean bugs' surprising diversity.

"The techniques used to identify microbes almost always miss the less common ones," Conley told

Normal microbe sampling is like choosing animals from a room filled with 1,000 dogs and only 3 cats, she said, and "if you pull 10 animals out of that crowd, they're all probably going to be dogs."

When most of the common bacteria (dogs) are gone, however, the remaining extreme bacteria (cats) thrive on the lack of competition and show up more readily in samples.

Planetary protection

To map the diversity of clean room microbes, biologists got on their hands and knees and swabbed large areas of NASA clean rooms across the nation.

Instead of trying to grow the unseen microbes, which is practically impossible to do, the scientists looked to a key genetic marker found in all bacteria called 16S ribosomal RNA.????

Like the method that genomics researcher Craig Venter has used to assess the diversity of bacteria in the world's oceans, Venkateswaran and his colleagues multiplied the genetic markers and decoded the sequences. The result? About 193 unique sequences--indicating 193 different bacterial "species"--were discovered, at least 13 of which were not known to science before.

Conley said the study will be crucial to sorting out the hitchhikers from the real thing during future searches for microbial life on other worlds.

"It's very useful information. We need to know what microbes a spacecraft is taking with it out into the solar system," she said. Conley added that NASA is now cataloging every possible organism it can find in clean rooms, as such a list of critters will help prevent a spacecraft from incorrectly confirming extraterrestrial life in the event that it detects some of its stowaways.

Conley said keeping NASA's facilities even cleaner is a growing priority to prevent "forward contamination" of other worlds during future missions.

"We want to do whatever we can to make sure we don't introduce life to places like Europa or Mars," Conley said.

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