One extremophile eats Martian dirt, survives in space and can create oxygen for colonies

Extremophiles are a favorite tool of astrobiologists. But not only are they good for understanding the kind of extreme environments that life can survive in, sometimes they are useful as actual tools, creating materials necessary for other life, like oxygen, in those extreme environments. A recent paper from Daniella Billi of the University of Rome Tor Vergata, published in pre-print form in Acta Astronautica, reviews how one particular extremophile fills the role of both useful test subject and useful tool all at once.

That extremophile is a cyanobacteria called Chroococcidiopsis. Unfortunately, biologists don’t have the same penchant for shortening names as astronomers do, but we will refer to it as Chroo so I don’t have to repeatedly copy and paste the name that I probably already spelled wrong. Chroo is native to the desert, with samples being found in Asia, North America, and even Antarctica, large parts of which are actually a desert, despite the persistent snow.

Given its rugged characteristics, several studies have already looked at different aspects of Chroo and the implications of how life might survive on other planets—or in outer space itself. Two experiments, the BIOlogy and Mars EXperiment (BIOMEX) and the much cooler sounding Biofilm Organisms Surfing Space (BOSS) experiment both used the Exposing Organisms to a Space Environment (EXPOSE) module on the ISS. You can tell we’re definitively back in space territory with all the acronyms.

Basically those experiments expose Chroo to the harshness of open space to see how well it survived. Each lasted about a year and a half. BIOMEX focused on individual cells, whereas BOSS focused on biofilms. Both experiments noted that UV radiation was the biggest killer of cells, and both noted that even some basic protection offered massive benefits to the cell underneath it. In BIOMEX’s case, that protection was provided by a thin layer of rock or regolith, while for BOSS, it came in the form of the top layer of cells in the biofilm sacrificing themselves and becoming a make-shift protective layer blocking UV from reaching the lower levels.

Perhaps even more impressively, when the Chroo was brought back to Earth after the BIOMEX experiment, they were rehydrated, since they had had their water removed before the experiment. But the scientists noticed that their DNA repair mechanisms were able to repair the DNA damage they had suffered. Even more impressively, there weren’t any increased mutations in future generations compared to a control strain that had stayed on Earth. In other words, Chroo’s DNA repair mechanisms were so effective they were able to recover from a year and a half of exposure to straight space radiation with no protection, and come back no worse for wear.

But space isn’t the only place to do these extremophile experiments. Several Earth-bound tests have been conducted as well. One experiment, which I can only assume was designed in an effort to create a bacterial Hulk, blasted a sample of Chroo with almost 24 kGy of gamma radiation—2,400 times the amount lethal to a human. Amazingly, the Chroo survived, though they didn’t turn into a green monster unfortunately.

Even higher levels of gamma radiation were used in another experiment, which did end up killing the Chroo, but monitored what they left behind. Biomarkers like carotenoids were still detectable even after the cyanobacteria had died, making them a good candidate for the search for extinct life on places like Mars.

A further Earth-bound test showed that Chroo could survive freezing temperatures like those that might be found on Europa or Enceladus. Reaching temperatures of -80C, the bacteria seemed to vitrify, leaving it in a dormant, glass-like state that it would wake up from once the conditions improved.

But that’s not all Chroo can do—it can live on lunar and Martian soil, and produce oxygen using only them and photosynthesis. It can even survive the high level of perchlorates found in the Martian soil, a tricky proposition for many Earth-based life forms, but “up-regulating” its DNA repair genes that counter the damage the perchlorates do.

Several future missions hope to study other aspects of this extremophile. They include CyanoTechRider, which will watch how microgravity affects Chroo’s DNA repair process. Another is BIOSIGN, which will try to power Chroo using far-infrared light, which it is capable of using for photosynthesis—a rare ability among cyanobacteria and plants more generally. Results from that experiment could inform our understanding of life around M-dwarf stars, which mainly emit infrared light.

Given all the abilities this super-cyanobacteria has, it seems well placed at the forefront of astrobiology research. Maybe that means someone will give it a shorter, catchier name to spare us poor space journalists from having to write it out every time we find something else cool about it.