Scientists have shown for the first time that one type of cyanobacteria Oxygen-producing and nitrogen-fixing can be efficiently grown in Mars at low pressure.
This makes it much easier to develop sustainable life support biological systems for humans on the red planet, according to a study published in Frontiers of Microbiology.
“Here we show that cyanobacteria can use gases available in the Martian atmosphere, at low total pressure, as their carbon and nitrogen source. Under these conditions, cyanobacteria maintained their ability to grow in water that contained only Mars-like dust and they could still feed other microbes. This could help make long-term missions to Mars sustainable, ”says lead author Dr Cyprien Verseux, an astrobiologist who directs the Applied Space Microbiology Laboratory at the University’s Center for Applied Space Technology and Microgravity (ZARM). from Bremen.
Cyanobacteria have long been considered candidates for boosting biological life support on space missions, as all species produce oxygen through photosynthesis, while some can fix atmospheric nitrogen in nutrients.
One difficulty is that they cannot grow directly in the Martian atmosphere, where the total pressure is less than 1% of that of Earth -6 to 11 hPa, too low for the presence of liquid water- while the partial pressure of nitrogen gas -0.2 to 0.3 hPa- is too low for your metabolism.
But recreating an atmosphere similar to Earth’s would be expensive: the gases would have to be imported, while the farming system would have to be robust – thus heavy for transport – to withstand the pressure differences. So the researchers sought a middle ground: an atmosphere close to that of Mars that allows cyanobacteria to grow well.
To find the right atmospheric conditions, Verseux and his collaborators developed a bioreactor called Atmos (Atmosphere tester for organic systems bound for Mars), in which cyanobacteria can be grown in artificial atmospheres at low pressure.
Any input must come from the Red Planet itself: apart from nitrogen and carbon dioxide, the gases abundant in the Martian atmosphere, and water that could be extracted from the ice, the nutrients must come from the “regolith,” the dust that covers planets and moons. similar to Earth. Martian regolith has been shown to be rich in nutrients like phosphorous, sulfur, and calcium.
Atmos has nine 1-liter containers made of glass and steel, each of which is sterile, heated, pressure-controlled, and digitally monitored, while the cultures inside are continuously agitated.
The authors chose a strain of nitrogen-fixing cyanobacteria called Anabaena because preliminary tests showed that it would be particularly good at using Martian resources and helping to cultivate other organisms. Closely related species have been shown to be edible, suitable for genetic engineering, and capable of forming specialized inactive cells to survive harsh conditions.
Verseux and his colleagues first cultivated Anabaena for 10 days under a mixture of 96% nitrogen and 4% carbon dioxide at a pressure of 100 hectoPascal (hPa), ten times lower than on Earth. Cyanobacteria grew as well as they did under ambient air. They then tested the combination of the regolith modified atmosphere.
Because no regolith has ever been brought back from Mars, they used a substrate developed by the University of Central Florida (called “Mars Global Simulant”) in place to create a growth medium. As controls, Anabaena was grown in standard medium, either in ambient air or under the same low pressure artificial atmosphere.
Cyanobacteria grew well in all conditions, even in regolith under the mixture rich in nitrogen and carbon dioxide at low pressure. As expected, they grew faster on a standard medium optimized for cyanobacteria than on Mars Global Simulant, in any atmosphere. But this is still a huge success: while the standard medium should be imported from Earth, regolith is ubiquitous on Mars. “We want to use the resources available on Mars as nutrients, and only those,” says Verseux.
The dry biomass of Anabaena was ground, suspended in sterile water, filtered and used successfully as a substrate for the growth of E. coli bacteria, demonstrating that sugars, amino acids and other nutrients can be extracted to feed other bacteria, which are less robust but proven tools for biotechnology.
For example, E. coli could be more easily modified than Anabaena to produce some food and drug products on Mars that Anabaena cannot.
The researchers conclude that oxygen-producing and nitrogen-fixing cyanobacteria can be efficiently grown on Mars at low pressure.