Biotech appropriate for the Red Planet

NASA, in collaboration with other major space agencies, aims to launch its first human missions to Mars in the early 2030s, while companies like SpaceX could do so even earlier. Astronauts on Mars need oxygen, water, food and other supplies. These must be found from Mars, as it would be impractical in the long run to bring them from Earth. In Boundaries in microbiology, scientists show for the first time that Anabaena cyanobacteria can be grown with only local gases, water, and other nutrients and at low pressure. This makes it much easier to develop sustainable biological life support systems.

“Here we show that cyanobacteria can use gases found in the Martian atmosphere, at low total pressures, as their source of carbon and nitrogen. Under these conditions, cyanobacteria maintained their ability to grow in water in dust was only similar to Mars and could still be used to feed other microbes. This could help make long-term missions to Mars sustainable, “says lead author Dr Cyprien Verseux , an astrobiologist in charge of the Laboratory of Applied Space Microbiology at the Center for Applied Space and Microgravity Technology (ZARM) of the University of Bremen, Germany.

Low pressure atmosphere

Cyanobacteria have long been targeted as candidates to guide biological life support on space missions, as all species make oxygen through photosynthesis while some are able to settling atmospheric nitrogen to nutrients. The problem is that they cannot grow directly in the Martian atmosphere, where the total pressure of less than 1% of the Earth’s soil – 6 to 11 hPa, is too low for meltwater to exist – while in which partial pressure of nitrogen gas – 0.2 to 0.3 hPa – is too low for the metabolism. But recreating an Earth-like atmosphere would be expensive: gases had to be imported, while the culture system had to be robust – hence heavy for goods – to resist the weight differences: “Think of a weight cooker,” Verseux says. So the researchers looked for a middle ground: an atmosphere near Mars that allows the cyanobacteria to grow well.

To find suitable atmospheric conditions, Verseux et al. developed a bioreactor called Atmos (for “Atmosphere Tester for Mars-bound Organic Systems”), in which cyanobacteria can be grown in artificial atmosphere at low pressure. Any input must come from the Red Planet itself: in addition to nitrogen and carbon dioxide, gases that are abundant in the Martian atmosphere, and water that could be mined from ice, it should nutrients come from “regolith”, the dust that covers Earth-like planets and branches. . Martian regolith has been shown to be rich in nutrients such as phosphorus, sulfur, and calcium.

Anabaena: a flexible cyanobacteria grown on Mars-like dust

Atmos has nine 1 L vessels made of glass and steel, each of which is sterile, heated, pressure-controlled, and digitally monitored, while the indoor cultures are continuously moved. The authors selected a type of nitrogen-fixing cyanobacteria called Anabaena sp. PCC 7938, as initial tests showed it would be particularly good at utilizing Martian resources and aiding the growth of other organisms. Species have been shown to be closely related to eating, suitable for genetic engineering, and able to form specific latent cells to survive in difficult conditions.

Verseux and his colleagues Anabaena first grew for 10 days under a mixture of 96% nitrogen and 4% carbon dioxide at a pressure of 100 hPa – ten times lower than on Earth. The cyanobacteria also grew under ambient air. They then tested the mixture of the modified atmosphere with regolith. Since regolith was never taken from Mars, they used a substrate developed by the University of Central Florida (known as the “Mars Global Simulant”) instead to create a growth medium. As controls, Anabaena was grown in a normal medium, either at ambient air or under the same low-pressure artificial atmosphere.

The cyanobacteria grew well under all conditions, forming a regolith under the full mixture of nitrogen and carbon dioxide at low pressure. As expected, they grew faster on a fully developed standard medium for cyanobacteria than on Mars Global Simulant, under all atmospheres. But this is still a great success: although a normal medium had to be imported from Earth, there is an ubiquitous regolith on Mars. “We want to use it as nutrients available on Mars, and just those,” Verseux said.

The biology of dried Anabaena was grounded, suspended in sterile water, filtered, and successfully used as a substrate for the growth of E. coli bacteria, proving that sugars, amino acids, and take other nutrients from them to feed other bacteria, which are not so small. hard but tested devices for biotechnology. For example, E. coli could be more easily invented than Anabaena to extract some food products and medicines on Mars that Anabaena cannot.

The researchers conclude that cyanobacteria can fix nitrogen, produce oxygen, grow effectively on Mars at low pressure under controlled conditions, with only localized materials.

Further changes to the pipeline

These results are significant improvements. But the authors warn that further studies are necessary: ​​”We want to go from this hypothesis to a system that can be used effectively on Mars,” Verseux says. tuning the optimal combination of weight, carbon dioxide and nitrogen for growth, while testing other genes of cyanobacteria, possibly genetically made for space missions. Also designed by Mars:

“Our bioreactor, Atmos, is not the cultivation system we would use on Mars: it is planned to test, on Earth, the conditions we would provide there. But our results will help to For example, the minimum weight means that we can develop a lighter structure that is easier to move, as we will not have to withstand large differences between the interiors. and the outside, ”Verseux concluded.

###

The project was funded by the Alexander von Humboldt Foundation.