Bacteria on the ISS have mutated into something never before seen on Earth

Movies and TV shows give the impression that space stations are aseptic and spotless. But everywhere there are people, there are all the bacteria that we bring with us. Bacteria have found niches on the International Space Station (ISS) and because they can evolve quite quickly, one species was seen to stand out from its terrestrial counterparts.

The bacteria in question are strains of Enterobacter bugandensis. This is an opportunistic pathogen, meaning it can only cause disease if the host is already “disturbed”, such as if it is already battling a disease or if it has a weakened immune system. The bacterium is known to be resistant to multiple drugs, meaning various antibiotic treatments are no longer effective in combating it. So it is important to understand how this bacterium orbits Earth.

In 2018, five strains of this bacterium were found on the ISS, and new work reports the existence of thirteen strains on the space station. While the previous analysis showed similarities, the more in-depth genetic research suggests that under the stress of such a unique environment, the ISS strains could have mutated in multiple ways to become both genetically and functionally distinct from the E. bugandensis that we find on earth.

“We have identified from our study certain genes that are exclusively present in organisms associated with the ISS, but not in their terrestrial counterparts,” the authors wrote in the paper.

Understanding how bacteria evolve in space is important to protect the health of astronauts and also to develop alternative approaches to combat these pathogens. In the case of these newly evolved species, their adaptation to microgravity could be hiding their Achilles heels.

“These genes could potentially serve as valuable targets for therapies against pathogenic microorganisms in the unique environment of the IS,” the authors continued.

The research team admits that there are some limitations in the genetic analysis, so they cannot say without a doubt that these species are the way they are because of space and space alone. Yet there is plenty of compelling evidence and even shows how these strains are integrated into communities of many different bacteria, some of which are also opportunistic pathogens resistant to multiple drugs.

This coexistence could be another factor that helped the organisms successfully find their niches in the ISS’s low-gravity, high-radiation, high-carbon dioxide environment.

The study has been published in the journal Microbiome.