On Sept. 4, 2025, a University of Houston lead team announced research showing that a bacterial species found in spacecraft clean rooms can survive intensive antimicrobial cleaning by going dormant. That’s important because other clean-room survivors had been known to live through disinfection by forming spores, which are thick-walled structures that protect bacteria from high temperatures or toxins such as ethanol.

The actinobacterium Tersicoccus phoenicis can’t form these spores, but the study published in the journal Microbiology Spectrum shows that it can go into a state similar to hibernation. In this state, it has no growth and almost no metabolism but has the ability to “wake up” when conditions improve.

While in this dormant state, T. phoenicis can’t be detected by the usual method of swabbing surfaces and checking which bacteria grow in culture from the swabs. That means it could theoretically sneak aboard spacecraft that are supposed to be free of Earth contaminants. If such a bug hitched a ride to another planet, it could wake up upon arrival and potentially disrupt existing extraterrestrial life. “It’s a huge planetary protection concern,” says Madhan Tirumalai, a biologist and biochemist at the University of Houston and lead author of the study.

T. phoenicis was first discovered in a clean room at National Aeronautics and Space Administration’s (NASA) Kennedy Space Center in Florida, where the Mars lander Phoenix was being prepared for launch. Two years later it popped up in a European Space Agency clean room in South America. In 2013 scientists discovered that this mystery survivor was not only a new species but a new genus of bacteria.

This species is part of a larger group of bacteria, known as actinomycetota or actinobacteria, that are able to go dormant when conditions aren’t conducive to growth. (One famous member of this group is Mycobacterium tuberculosis, the bacterium that causes tuberculosis, which can go dormant and persist in the lungs over a lifetime.) To learn whether T. phoenicis was capable of dormancy, Tirumalai and his colleagues deprived cells of nutrients and extracted all water from them (a process called desiccation). The cells stopped growing, and the number of viable cells plummeted within days.

To show that these nonviable cells were dormant, not dead, the researchers added a protein called a resuscitation-promoting factor (Rpf), which is known to “wake up” other species of dormant actinobacteria. The Rpf revived the cells, “proving they were alive but silent,” Tirumalai says.

It’s not yet clear how to effectively clean up dormant microbes. Tirumalai and his colleagues are now looking to test other clean-room survivors for their dormancy potential, which would make a case for upending current cleaning procedures. “If we can show that a significant number of these organisms that have been isolated from clean rooms can go into dormancy,” Tirumalai says, “bingo—we have a much bigger story.”