It doesn't seem logical for life to be able to survive in space, at least for long. There's nothing to breathe or feed on, the temperatures can swing quickly by hundreds of degrees, and the radiation is intense. Yet we know some bacterial spores manage to cling to the outside of the International Space Station and live, we just don't know how they do it. Now, new research takes us a little closer.
Professor George Fox of the University of Houston sequenced the genome of a Bacillus bacterial species, B. safensis FO-36bT, found to have made it into the cleanrooms of the Jet Propulsion Laboratory, despite all the work done to keep them out. Bacillus produce spores as part of their reproductive cycle that can survive harsh conditions before reviving when things improve.
Fox compared FO-36bT and partial sequences of two strains, B. pumilus SAFR-032 and B. safensis JPL-MERTA-8-2 – which have also been found to survive NASA's anti-contamination measures – with B. pumilus ATCC7061T, a strain known not to survive the treatments NASA uses to discourage microbial hitchhikers.
JPL-MERTA-8-2 gets its initials from having been found aboard the Mars Odyssey Spacecraft and the Mars Explorer Rover pre-launch. It's also the only species so far shown to grow better in the microgravity of space than it does on Earth, although an improved capacity to fight off antibiotics is more widespread.
In BMC Microbiology, Fox announces many genetic differences between FO-36bT and ATCC7061T, including 10 genes that were not present in any of the other strains. At this stage, it is not clear which genes, alone or in combination, explain the ability of these strains' spores to resist the radiation and hydrogen peroxide NASA uses to kill bacteria in an attempt to sterilize their spacecraft. However, Fox hopes further study will not only identify the crucial sequences but reveal if they are being passed between strains.
All the strains are harmless to humans, but the quest to understand the survival of bacteria in space is important for at least two reasons. For one, we want to be very careful about taking anything living to worlds we visit, particularly if they could already have life of their own.
"The search for life elsewhere is impacted by the possible transport of organisms from Earth to solar system bodies of interest," Fox said in a statement.
Additionally, there is the question of whether life can catch a lift aboard a rock that is knocked into space from the impact of a larger asteroid and survive both the long journey between planets and re-entry. If so, it could have important implications for how common life is in the universe, with a single point of origin seeing many worlds.