Radiation-resistant bacteria survived in ISS for 3 years, raises hope of withstanding travel to Mars: Study

The red-colored bacteria named Deinococcus has entered the Guinness Book of World Records for being the most radiation-resistant organisms in the world


                            Radiation-resistant bacteria survived in ISS for 3 years, raises hope of withstanding travel to Mars: Study
The International Space Station (JAXA/NASA)

Some microorganisms live in extremes. They can resist harmful UV radiation and tolerate intense heat, cold and acidic environments. It is this quality that has enabled one such extremophile to survive three years in the International Space Station (ISS), about 400 km above Earth, according to a new study. It may also have the potential to withstand travel to Mars.

The extremophile in question is a type of red-colored bacteria named Deinococcus. It has earned its place in the Guinness Book of World Records for being the most radiation-resistant organism on Earth. It can survive and multiply when exposed to radiation doses that are lethal to others, including humans. Other extremophiles may be able to achieve this feat too. "Our colleagues have tested cyanobacterium [microbes that can also endure extreme conditions], and the results will be published soon," Dr Akihiko Yamagishi, from Tokyo University of Pharmacy and Life Sciences, told MEA WorldWide (MEAWW). He added that they are likely to test other extremophiles in the future.

The findings support a theory that explains the origins of life: panspermia. It proposes that microbes can originate from any part of the cosmos, and may seed life across the universe by hitching a ride on meteorites or comets. It also suggests that they can tolerate the long and arduous journey in outer space, resisting harsh conditions such as vacuum, temperature fluctuations, and radiations. But not everyone agrees with the theory due to some inconsistencies, according to Dr Yamagishi. "Some think the emergence of life is very rare and happened only once in the Universe, while others think the emergence of life is very easy and can happen on every planet that is suitable for life," he explained. "If panspermia is possible, life must exist much more often."

The bacterial exposure experiment took place from 2015 to 2018 using the Exposed Facility located on the exterior of Kibo, the Japanese Experimental Module of the International Space Station (JAXA/NASA)

Dr Yamagishi is the principal investigator of the space mission named Tanpopo. It is tasked with testing the panspermia theory. In 2018, the researchers detected Deinococcus in the atmosphere 12 km above Earth. This discovery prompted a question: could they withstand outer space conditions long enough to support panspermia? The team designed an experiment testing whether Deinococcus can survive in the ISS. They dried bacterial cells, clumping them together as pellets or aggregates. They placed them in aluminum plates attached outside of the ISS, exposing them to the space conditions. "We have measured the survival fraction after one-, two- and three-year exposure in space," Dr. Yamagishi explained.

After three years, the team saw that their survival relied on the thickness of the bacterial aggregates. Pellets thicker than 0.5 mm survived. Though the bacteria on the outer surface perished, they managed to shield those beneath them. They also predicted that an aggregate measuring 1 mm is likely to survive in outer space for up to eight years. "The results suggest that radioresistant Deinococcus could survive during the travel from Earth to Mars and vice versa," Dr Yamagishi said.

These findings have set the stage for taking the radioresistant bacteria further into space. "We are looking for the opportunity to do a similar experiment outside Van Allen belt [25 000 to 45 000 km above Earth], and near the Moon, Dr Yamagishi noted. "We are also looking for the opportunity to search for life on Mars, building an automatic microscope to search for bacteria on Mars' surface."

The study is published in Frontiers in Microbiology.

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