Researchers find four strains of bacteria on the ISS — three are completely new to science

Life finds a way, the old saying goes. According to a new paper, that includes ‘living on a spaceship’.

Transmission electron micrograph of strain S2R03-9T Methylobacterium jeotgali, a relative of the new strains. Image via Wikimedia.

A team of researchers from India and the US working in collaboration with NASA report discovering four bacterial strains living on the International Space Station (ISS). Three of these were completely unknown to science until now. Three of these strains were isolated in 2015 and 2016 — one in an overhead panel in a research lab, the second in the station’s Cupola, and the third on the surface of the crew’s dining table. The fourth strain was isolated from an old HEPA filter that was brought back to Earth in 2011.

All of these strains belong to a ‘good’ family of bacteria found in soil and freshwater here on Earth. They’re involved in nitrogen fixation processes, plant growth, and in fighting plant pathogens.

Out of this world

These bacteria likely made their way onto the ISS when the crew first started growing a small number of plants aboard to supplement their diets. Plants don’t develop and live on their own, but generally rely on bacterial communities for several essential services; as such, finding plant-related microbes in their environment (the space station) isn’t very surprising.

However, only one of these was previously identified by researchers: the one from the used HEPA filter. This strain was identified as belonging to the species Methylorubrum rhodesianum. The other three were genetically sequenced and found to all belong to the same, new species. They were temporarily christened IF7SW-B2T, IIF1SW-B5, and IIF4SW-B5.

The team, led by University of Southern California geneticist Swati Bijlani, proposes the name Methylobacterium ajmalii for the species, after Indian biodiversity scientist Ajmal Khan. The new species is closely related to the already-known M. indicum bacteria. The genetic sequencing of these bacteria was meant to help us better determine how they relate to other bacteria, but also to help us determine the genetic elements that make them suited to life in the unusual conditions aboard the ISS.

“To grow plants in extreme places where resources are minimal, isolation of novel microbes that help to promote plant growth under stressful conditions is essential,” Kasthuri Venkateswaran and Nitin Kumar Singh from NASA’s JPL, two members of the team, explained in a press statement.

“The whole-genome sequence assembly of these three ISS strains reported here will enable the comparative genomic characterization of ISS isolates with Earth counterparts in future studies,” the team explains in their study. “This will further aid in the identification of genetic determinants that might potentially be responsible for promoting plant growth under microgravity conditions and contribute to the development of self-sustainable plant crops for long-term space missions in future.”

At least one of the strains, IF7SW-B2T, shows promise in our search for genes involved in plant growth, they add. Still, we’re only just beginning to understand the wealth of bacteria living aboard the ISS. Collecting samples isn’t hard, but taking them to Earth for proper examination is. The crew has taken over 1,000 samples so far, but they’re all still awaiting transport back to Earth.

The paper “Methylobacterium ajmalii sp. nov., Isolated From the International Space Station” has been published in Frontiers in Microbiology.

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