在近地轨道模拟火星条件下的荒漠蓝藻：对火星可居性的启示。

A Desert Cyanobacterium under Simulated Mars-like Conditions in Low Earth Orbit: Implications for the Habitability of Mars.

机构信息

1 University of Rome Tor Vergata, Department of Biology, Rome, Italy.

2 German Aerospace Center, Institute of Planetary Research, Management and Infrastructure, Astrobiological Laboratories, Berlin, Germany.

出版信息

Astrobiology. 2019 Feb;19(2):158-169. doi: 10.1089/ast.2017.1807.

DOI:10.1089/ast.2017.1807

PMID:30742497

Abstract

In the ESA space experiment BIOMEX (BIOlogy and Mars EXperiment), dried Chroococcidiopsis cells were exposed to Mars-like conditions during the EXPOSE-R2 mission on the International Space Station. The samples were exposed to UV radiation for 469 days and to a Mars-like atmosphere for 722 days, approaching the conditions that could be faced on the surface of Mars. Once back on Earth, cell survival was tested by growth-dependent assays, while confocal laser scanning microscopy and PCR-based assay were used to analyze the accumulated damage in photosynthetic pigments (chlorophyll a and phycobiliproteins) and genomic DNA, respectively. Survival occurred only for dried cells (4-5 cell layers thick) mixed with the martian soil simulants P-MRS (phyllosilicatic martian regolith simulant) and S-MRS (sulfatic martian regolith simulant), and viability was only maintained for a few hours after space exposure to a total UV (wavelength from 200 to 400 nm) radiation dose of 492 MJ/m (attenuated by 0.1% neutral density filters) and 0.5 Gy of ionizing radiation. These results have implications for the hypothesis that, during Mars's climatic history, desiccation- and radiation-tolerant life-forms could have survived in habitable niches and protected niches while transported.

摘要

在欧洲航天局（ESA）的 BIOMEX（生物学和火星实验）太空实验中，干燥的 Chroococcidiopsis 细胞在国际空间站的 EXPOSE-R2 任务中暴露于类似火星的条件下。这些样本暴露于 UV 辐射下 469 天，并暴露于类似火星的大气中 722 天，接近在火星表面可能面临的条件。返回地球后，通过依赖生长的测定法测试细胞存活情况，同时使用共聚焦激光扫描显微镜和基于 PCR 的测定法分别分析光合色素（叶绿素 a 和藻胆蛋白）和基因组 DNA 中累积的损伤。只有在与火星土壤模拟物 P-MRS（层状火星风化层模拟物）和 S-MRS（硫酸盐火星风化层模拟物）混合的干燥细胞（4-5 细胞层厚）中才发生存活，并且在暴露于总 UV（波长为 200 至 400nm）辐射剂量为 492MJ/m（通过 0.1%中性密度滤光片衰减）和 0.5Gy 电离辐射后，仅能维持数小时的活力。这些结果对以下假设具有重要意义，即在火星的气候历史中，耐干燥和辐射的生命形式可能在可居住的小生境和受保护的小生境中得以存活，并在运输过程中得以保护。