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A year in space is not a walk in the park. Just ask Scott Kelly, the American astronaut who spent a year on the International Space Station (ISS) in 2015.
His long stay in space changed his DNA, telomeres and gut microbiome, he lost bone density and three months later his feet were still sore.
But it is quite another thing to survive in bare space outside the ISS ‘protection, where UV rays, vacuum, enormous temperature fluctuations and microgravity are all imminent threats.
So, it’s a real feat that some kind of bacterium first found in a jar of meat, Deinococcus radiodurans, was still alive and well after a year of living on a specially designed platform outside the ISS pressurized module.
Researchers have been studying these powerful microbes for a while; In 2015, an international team established the Tanpopo mission outside the Japanese Kibo experimental module to test resistant bacterial species.
Now, D. radiodurans passed with flying colors.
The bacterial cells were dehydrated, shipped to the ISS and placed in the Exposed Facility, a platform continuously exposed to the space environment; in this case, the cells were behind a glass window that blocked UV light at wavelengths below 190 nanometers.
“The results presented in this study may raise awareness of planetary protection issues, for example, the Martian atmosphere absorbing UV radiation below 190-200 nm,” the team from Austria wrote in their new paper. , Japan and Germany.
“To mimic this condition, our experimental setup on the ISS included a silicon dioxide glass window.”
This is not the longest period D. radiodurans it was kept in this condition – in August we wrote about a sample of the bacterium that had been up there for three whole years.
But the team wasn’t trying to break a world record, instead they were trying to find out what it does D. radiodurans just so good at surviving in these extreme conditions.
SEM images of D. radiodurans control (left) and after exposure LEO (right). (Ott et al., Microbiome, 2020)
Then, after a year of radiation, freezing and boiling temperatures, and zero gravity, the researchers brought back space-traveling bacteria to Earth, rehydrated both a control that had spent the year on Earth and the Low Earth sample. Orbit (LEO), and they compared their results.
The survival rate was much lower for the LEO bacteria than the control version, but the bacteria that survived appeared to be fine, even if they had become slightly different from their Earth-related brothers.
The team found that LEO bacteria were covered with small bumps or vesicles on the surface, numerous repair mechanisms had been activated, and some proteins and mRNAs had become more abundant.
The team isn’t exactly sure why the vesicles (which you can see in the photo above) formed, but they have a couple of ideas.
“Intensified blistering after recovery from LEO exposure may serve as a rapid response to stress, which increases cell survival by withdrawing stress products,” the team wrote.
“In addition, the outer membrane vesicles may contain proteins important for nutrient acquisition, DNA transfer, toxin transport and quorum sensing molecules, triggering the activation of resistance mechanisms after exposure. to space “.
This type of study helps us understand whether bacteria could survive other worlds, and perhaps even the journey between them, which will become increasingly important as we humans and the germs we carry with us begin to travel farther than our Moon. in the Solar System, and one day maybe even beyond.
“These investigations help us understand the mechanisms and processes by which life can exist beyond the Earth, expanding our knowledge of how to survive and adapt to the hostile environment of space,” said University of Vienna biochemist Tetyana Milojevic. .
“The results suggest that the survival of D. radiodurans in LEO for a longer period is possible thanks to its efficient molecular response system and indicates that even the longest and most distant journeys are feasible for organisms with such capabilities. “
The research was published in Microbiome.
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