Nitrogen cycle microorganisms can be reactivated after Space exposure.

Area of Science:

• Astrobiology
• Microbial Biotechnology
• Space Life Support Systems

Background:

• Long-term human space missions require regenerative life support systems (RLSS).
• Microbial biotechnology is crucial for nitrogen conversion in RLSS, producing desirable products like nitrate or nitrogen gas.
• Reactivating microbial cells after exposure to space conditions (microgravity and radiation) is essential for bioreactor operation.

Purpose of the Study:

• To assess the feasibility of reactivating microorganisms involved in nitrogen cycle conversions after spaceflight.
• To evaluate the impact of space exposure on the nitrogen conversion efficiency of microbial communities.
• To determine optimal storage strategies for microbial cultures intended for space applications.

Main Methods:

• Microorganisms for nitrogen cycle conversions were exposed to space conditions (microgravity and radiation) during a 44-day FOTON-M4 spaceflight.
• Post-flight, axenic cultures and defined microbial communities were reactivated.
• Nitrogen conversion rates were measured and compared to terrestrial controls.

Main Results:

• All tested microbial cultures and communities, including ureolytic bacteria, ammonia oxidizers, nitrite oxidizers, denitrifiers, and anammox bacteria, were successfully reactivated after space exposure.
• Space-exposed cultures generally exhibited similar or higher nitrogen conversion rates compared to terrestrial preservation at similar temperatures.
• Terrestrial storage at 4°C resulted in the highest nitrogen conversion rates, suggesting refrigeration as a beneficial strategy for space-exposed cultures.

Conclusions:

• Microbial communities essential for nitrogen cycling can be reactivated after exposure to space conditions.
• Refrigerated space exposure is a promising strategy to maintain microbial activity for RLSS.
• The demonstrated combined potential of ureolysis, nitritation, nitratation, denitrification, and anammox is a key enabler for resource recovery in human space exploration.