Four species of bacteria – including three previously unknown to science – were discovered aboard the International Space Station (ISS), asking questions about how they got there and how they managed to survive.
Their discovery could also bolster future efforts to grow crops on long space flight missions, as related species are known to promote plant growth and help them fight pathogens.
Previous studies had suggested that certain resistant strains of bacteria could survive the harsh conditions of space, including the dried granules of Deinococcus the bacteria – listed in Guinness World Records as the most resistant in the world – that survived the surface of the space station for three years. They were deliberately placed there to test the “panspermia” theory, according to which life exists throughout the universe and can be transported between planets by space dust, asteroids, comets, or even contaminated spaceships.
Another recent study identified a diverse population of bacteria and fungi associated with the human body inside the ISS, where they are somewhat more protected – although still subject to low gravity, recirculated air, and to high levels of carbon dioxide.
The new bacteria were similarly identified from samples taken from various locations inside the ISS. One was discovered on a dining table; another on a hanging panel in a research area used to study low gravity; the third in the Cupola observatory. The fourth species, which was already known, was found on an old air-purifying filter, which had been returned to Earth. All are rod-shaped bacteria belonging to the Methylobacteria family – typically found in soil and freshwater, where they help promote plant growth and defend against pathogens.
They are more likely to have been transferred to the ISS from Earth – rather than coming from space – and have either survived since the station was established or were introduced when new astronauts or payloads arrived. .
Christine Moissl-Eichinger, a microbiologist at the Medical University of Graz, Austria, said: “All the microbes in the ISS come from the Earth. There are astronauts and cargo is being traded all the time. None of these items are completely sterile. “
It is important to understand the types of microbes that can accumulate, survive, and even thrive in this unique environment, as they can affect the health of the crew, the structure of the spacecraft, or contaminate the planets and astronomical bodies that they visit.
“Since these ISS strains have been isolated at different times and in various locations, their persistence in the ISS environment and their ecological significance in closed systems warrant further study,” wrote the American-Indian team that carried out the analysis, which was published in Frontières en microbiologie.
Methylorubrum rhodesianum was the bacteria found that was already known to science. The other three had never been identified before, but genetic and taxonomic analysis suggests that they are related to Methylobacterium indicum, a bacteria sometimes found on rice grains. The researchers said the bacteria could provide “biotechnologically useful genetic determinants” for growing crops in space. “To grow plants in extreme locations where resources are scarce, isolating new microbes that help promote plant growth under stressful conditions is essential.”
However, Moissl-Eichinger cautioned against the excitement of the discovery. The fact that these microbes have never been described before by science does not necessarily mean that they are important. She said: “In every spoon of soil or stool sample, there are hundreds of undescribed microbial species. I’m sure there are still hundreds, if not thousands of less characterized, if not unknown, microorganisms on board the ISS.
“This [finding] is of course quite interesting, because one day we intend to send humans on a long trip to Mars, and they will be locked up with billions of microbes. The more we know about all of these different species, the better. “