The menagerie of bacterial and fungal species living among us is ever growing — and this is no exception in low-gravity environments such as the International Space Station.
A new study showed that researchers from the US and India working with NASA have discovered four strains of bacteria living in different places on the ISS. Three of these strains were, until now, completely unknown to science.
Most of the microbes were identified in 2015 and 2016 — one was found on an overhead panel of the ISS research station; another in the Cupola, an observation and work area for the ISS crew; and the third appeared on the surface of the station's dining table.
The fourth was found in an old HEPA air filter that returned to Earth in 2011.
All four strains belong to a family of bacteria found in soil and freshwater. These bacteria are involved in nitrogen fixation and plant growth, and can help fight off plant pathogens. Basically, excellent microbes to have around if you're growing things.
You might wonder what such soil bacteria were doing all the way up on the ISS, but the astronauts living in the space station have been growing small amounts of food for years, so it's unsurprising that scientists found plant-related microbes aboard.
The study authors genetically sequenced the microbes and found that three of them belonged to the same previously unidentified bacteria species. The three strains were named IF7SW-B2T, IIF1SW-B5, and IIF4SW-B5.
They identified the fourth strain — the HEPA-filter find — as a known microbial species called Methylorubrum rhodesianum.
The research team — led by Swati Bijlani, a geneticist at the University of Southern California — has proposed calling the new bacteria species Methylobacterium ajmalii after Ajmal Khan, a renowned Indian biodiversity scientist. This new species is closely related to an existing species named Methylobacterium indicum.
Identifying genes that help microbes survive in microgravity
Considering these microbes can survive aboard the ISS, Bijlani's team set out to identify which genes in each of the four bacteria strains could be used to help promote plant growth in the low-gravity conditions of space.
"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," the authors of the new study wrote.
The team found that one of the strains — IF7SW-B2T — had genes involved in plant growth. One of IF7SW-B2T's genes helps code for an enzyme essential to producing cytokinin, a plant hormone that promotes cell division in roots and shoots.
The researchers said that they've barely scratched the surface of microbial diversity on the space station. Around 1,000 samples have already been collected on the ISS, but they are still waiting to return to Earth.
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