Cortesão Marta, Siems Katharina, Koch Stella, Beblo-Vranesevic Kristina, Rabbow Elke, Berger Thomas, Lane Michael, James Leandro, Johnson Prital, Waters Samantha M, Verma Sonali D, Smith David J, Moeller Ralf
Aerospace Microbiology Research Group, Department of Radiation Biology, Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany.
Astrobiology Research Group, Department of Radiation Biology, Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany.
Front Microbiol. 2021 Feb 22;12:601713. doi: 10.3389/fmicb.2021.601713. eCollection 2021.
Whether terrestrial life can withstand the martian environment is of paramount interest for planetary protection measures and space exploration. To understand microbial survival potential in Mars-like conditions, several fungal and bacterial samples were launched in September 2019 on a large NASA scientific balloon flight to the middle stratosphere (∼38 km altitude) where radiation levels resembled values at the equatorial Mars surface. Fungal spores of and bacterial cells of , subsp. , and sp. MASE-IM-9 were launched inside the MARSBOx (Microbes in Atmosphere for Radiation, Survival, and Biological Outcomes Experiment) payload filled with an artificial martian atmosphere and pressure throughout the mission profile. The dried microorganisms were either exposed to full UV-VIS radiation (UV dose = 1148 kJ m) or were shielded from radiation. After the 5-h stratospheric exposure, samples were assayed for survival and metabolic changes. Spores from the fungus and cells from the Gram-(-) bacterium were the most resistant with a 2- and 4-log reduction, respectively. Exposed sp. MASE-IM-9 was completely inactivated (both with and without UV exposure) and subsp. only survived the UV shielded experimental condition (3-log reduction). Our results underscore a wide variation in survival phenotypes of spacecraft associated microorganisms and support the hypothesis that pigmented fungi may be resistant to the martian surface if inadvertently delivered by spacecraft missions.
陆地生命能否承受火星环境，对于行星保护措施和太空探索至关重要。为了解微生物在类火星条件下的生存潜力，2019年9月，几个真菌和细菌样本搭载美国国家航空航天局（NASA）的一个大型科学气球升至平流层中部（约38千米高空），那里的辐射水平与火星赤道表面的值相似。在整个任务过程中，将球孢枝孢（Cladosporium sphaerospermum）的真菌孢子以及嗜麦芽窄食单胞菌（Stenotrophomonas maltophilia）、嗜麦芽寡养单胞菌（Stenotrophomonas rhizophila）亚种和MASE-IM-9芽孢杆菌（Bacillus sp. MASE-IM-9）的细菌细胞置于装有模拟火星大气和压力的MARSBOx（用于辐射、生存和生物学结果实验的大气微生物）有效载荷内。干燥的微生物要么暴露于全紫外-可见光辐射（紫外线剂量 = 1148 kJ/m²），要么受到辐射屏蔽。在平流层暴露5小时后，对样本进行生存和代谢变化分析。真菌球孢枝孢的孢子和革兰氏阴性菌嗜麦芽窄食单胞菌的细胞抗性最强，分别减少了2个对数和4个对数。暴露的MASE-IM-9芽孢杆菌完全失活（无论有无紫外线照射），嗜麦芽寡养单胞菌亚种仅在紫外线屏蔽实验条件下存活（减少3个对数）。我们的结果强调了航天器相关微生物生存表型的广泛差异，并支持以下假设：如果航天器任务无意中携带，有色真菌可能对火星表面具有抗性。
