Dried biofilms of Chroococcidiopsis sp. CCMEE 029 were revived after a 672-day exposure to space vacuum outside the International Space Station during the EXPOSE-R2 space mission. After retrieval, they were air-dried stored for 3.5 years. Space vacuum reduced cell viability and increased DNA damage compared to air-dried storage for 6 years under laboratory conditions. Long exposure times to space vacuum and extreme dryness decrease the changes of survival that ultimately depend on DNA damage repair upon rehydration, and hence, an in silico analysis of Chroococcidiopsis sp. CCMEE 029's genome was performed with a focus on DNA repair pathways. The analysis identified a high number of genes that encode proteins of the homologous recombination RecF pathway and base excision repair that were over-expressed during 1 and 6 h rehydration of space-vacuum exposed biofilms. This suggests that Chroococcidiopsis developed a survival strategy against desiccation, with DNA repair playing a key role, which allowed the revival of biofilms exposed to space vacuum. Unravelling how long anhydrobiotic cyanobacteria can persist under space vacuum followed by prolonged air-dried storage is relevant to future astrobiological experiments that use space platforms and might require prolonged air-dried storage of the exposed samples before retrieval to Earth.

中文翻译：

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暴露于太空真空和长期干燥的无水蓝藻生物膜的复兴：对未来低地球轨道以外任务的影响

Chroococcidiopsis sp. 的干燥生物膜。在 EXPOSE-R2 太空任务期间，CCMEE 029 在国际空间站外的太空真空中暴露 672 天后复活。取出后，将它们风干存放 3.5 年。与在实验室条件下风干储存 6 年相比，空间真空降低了细胞活力并增加了 DNA 损伤。长时间暴露于空间真空和极度干燥会减少最终依赖于补水时 DNA 损伤修复的生存变化，因此，对Chroococcidiopsis进行了计算机分析sp. CCMEE 029 的基因组研究重点是 DNA 修复途径。该分析确定了大量编码同源重组 RecF 途径和碱基切除修复蛋白的基因，这些基因在暴露于真空的生物膜的 1 和 6 小时再水化过程中过度表达。这表明Chroococcidiopsis开发了一种对抗干燥的生存策略，其中 DNA 修复起着关键作用，这使得暴露于太空真空的生物膜得以恢复。解开无水生物蓝藻在空间真空下可以持续多长时间，然后长时间风干存储与未来使用空间平台的天体生物学实验相关，并且可能需要在取回地球之前长时间风干存储暴露的样本。