Bacteria on board the International Space Station (ISS) have evolved new traits in order to survive in low Earth orbit, and some show signs of increased virulence.
Microbes from Earth have made their way to the station via human hosts and the regular delivery of equipment and supplies.
NASA has been monitoring the ISS鈥檚 microbiome for a decade to understand how microbes survive in space conditions and what threat they might pose to astronauts鈥� health.
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In recent years, researchers have isolated numerous unique strains of bacteria from the ISS with genetic changes that seem to offer protection against the increased radiation and weightlessness experienced aboard the station.
In the latest study, at NASA鈥檚 Jet Propulsion Laboratory in California and his colleagues studied newly discovered bacterial species found in ISS samples: Microbacterium mcarthurae, Microbacterium meiriae, Paenibacillus vandeheii, Arthrobacter burdickii and Leifsonia williamsii. They sequenced the genomes of the bacteria and聽compared them with their nearest known relatives on Earth.
鈥淥ur study shows that the microorganisms we isolated from the International Space Station have uniquely adapted to survive in space when compared to the Earth counterparts,鈥� says Venkateswaran.
The adaptations found in ISS microbes include proteins that help them cope with microgravity and improved ways to repair their DNA, which can be damaged by radiation exposure in space.
鈥淭hese microbes have found ways to live and possibly even thrive in space, and understanding how they do this could have big benefits for space exploration and health,鈥� says Venkateswaran.
So far, it is unclear what threat these bacteria pose to astronauts鈥� health, but Venkateswaran and his colleagues say that some of the genetic traits they identified suggest potential pathogenic capabilities. The ISS species show enhanced activity of certain genes linked to bacterial virulence, including those that help them evade and damage the immune system. They can also form biofilms: slimy layers that stick to surfaces and can help bacteria resist antibiotics and disinfectants.
The findings suggest astronauts will need to make more effort to control moisture inside spacecraft to prevent the growth of biofilms, the researchers say.
The team also suggests that the identified genetic traits could become targets for new drugs if these microorganisms turn out to harm humans.
鈥淢onitoring the microbial population on board the human habitats in long missions and characterising their genetic traits are crucial for safeguarding astronaut health,鈥� says Venkateswaran.
鈥淪pace is a new environment for those of us interested in extremophile bacteria,鈥� says at the University of New South Wales in Sydney, Australia.
He says the findings on virulence are 鈥渘ot necessarily alarming鈥�, but it is hard to predict the future and the work highlights the importance of monitoring microbes on space voyages and taking countermeasures to manage any that may threaten health.
鈥淲e are still surprised daily by the diversity of life and the conditions that it can tolerate,鈥� says Baker.
bioRxiv
