How a bacterial species in extraterrestrial kombucha cultures can survive outer space

When Kombucha cultures were blasted into space and sent to the International Space Station (ISS) it wasn’t so health-conscious astronauts could make a refreshing drink, according to a new study published in Frontiers in Microbiology.

Although the challenges of growing food in space are well documented (space lettuce, anyone?), scientists sent the cultures up there in 2014 to investigate the survival of the kombucha microbial species under space conditions.

Here on Earth, it’s grown and sold as a drink produced from fermenting sugared tea with a kombucha symbiotic culture of bacteria and yeast (SCOBY) – also called the kombucha multimicrobial community (KMC).

The KMC cultures were attached to the outside of the ISS and subjected to the vacuum of space and to simulated Mars-like conditions for 18 months. Then they were brought back and reactivated on Earth.

Researchers found that while the microbial ecology of the kombucha culture was destroyed, a cellulose-producing bacterial genus survived and the genome of one of its key species remained stable, most likely due to its protective biofilm.

“Based on our metagenomic analysis, we found that the simulated Martian environment drastically disrupted the microbial ecology of kombucha cultures,” says co-author Bertram Brenig, professor of molecular biology of livestock and director of the Institute of Veterinary Medicine at the University of Göttingen, Germany.

“However, we were surprised to discover that the cellulose-producing bacteria of the genus Komagataeibacter survived.”

This is the first evidence that bacterial cellulose could be a biomarker for life in outer space, and suggests that cellulose-based membranes or films could be a promising biomaterial for protecting life and producing consumer goods in off-Earth settlements.

Why send kombucha microbes to space?

The original kombucha culture used in this study was maintained in filter-sterilised black tea (Lipton to be exact) with white sugar, but a dehydrated KMC biofilm was sent to the ISS.

Scientists wanted to understand the capability of organisms to survive the harsh conditions in outer space, including exposure to cosmic radiation, microgravity, temperature extremes, and the vacuum.

As part of European Space Agency’s Expose-R2 project, 46 species of bacteria, fungi and arthropods were delivered by a Progress supply ship to the International Space Station in July 2014. Spacewalking cosmonauts Alexander Skvortsov and Oleg Artemyev attached the package to the outside of the Zvezda module on 18 August 2014, where it stayed until it was retrieved 18 months later.

They subjected the KMC to these conditions using the EXPOSE-R2 platform – a miniature photochemistry laboratory installed on the outside of the International Space Station (ISS).

After 18 months of exposure, the samples were brought back to Earth, reactivated and cultivated for two years. The surviving bacterial genomes were then sequenced to understand genome stability under extraterrestrial conditions by comparing them with a ground-based culture.

A diagram of the workflow methodology of the study, from original kombucha microbial community to genome sequencing.
Workflow of the study’s methods. Credit: Santana de Carvalho et al (2022) DOI:10.3389/fmicb.2022.782175

“Our results show that K. oboediens was able to survive being exposed to the space environment for 18 months and that its genome remains mainly conserved after spaceflight,” they say.

In fact, the genetics behind cellulose synthesis, nitrogen-fixation, hopanoid lipids biosynthesis, and stress-related pathways were not affected, and only minor changes were observed in central carbohydrate and energy metabolism pathways.

Because its metabolic pathways remained unaffected, the authors say that this species may have potential for space applications: “This suggests that K. oboediens is a strong candidate for cellulose production in Mars colonies’ industry.”

According to the researchers, the ability of K. oboediens to maintain its genome’s stability and functionality when exposed to the space environment is either due to a recovery of most of its functions after successive cultures in the lab back on Earth, or due to the protective role of the cellulose-based KMC biofilm in space.

So, the KMC biofilm needs future research to explore its potential for space-related technologies.

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