He Lin, Wang Shiwei, Cortesão Marta, Wu Muying, Moeller Ralf, Setlow Peter, Li Yong-Qing
1School of Electrical Engineering and Intelligentization, Dongguan University of Technology, Dongguan, Guangdong China.
2Department of Physics, East Carolina University, Greenville, North Carolina 27858-4353 USA.
NPJ Microgravity. 2018 Dec 4;4:26. doi: 10.1038/s41526-018-0059-7. eCollection 2018.
Outer space is a challenging environment for all forms of life, and dormant spores of bacteria have been frequently used to study the survival of terrestrial life in a space journey. Previous work showed that outer space vacuum alone can kill bacterial spores. However, the responses and mechanisms of resistance of individual spores to space vacuum are unclear. Here, we examined spores' molecular changes under simulated space vacuum (~10 Pa) using micro-Raman spectroscopy and found that this vacuum did not cause significant denaturation of spore protein. Then, live-cell microscopy was developed to investigate the temporal events during germination, outgrowth, and growth of individual spores. The results showed that after exposure to simulated space vacuum for 10 days, viability of spores of two species was reduced up to 35%, but all spores retained their large Ca-dipicolinic acid depot. Some of the killed spores did not germinate, and the remaining germinated but did not proceed to vegetative growth. The vacuum treatment slowed spore germination, and changed average times of all major germination events. In addition, viable vacuum-treated spores exhibited much greater sensitivity than untreated spores to dry heat and hyperosmotic stress. Among spores' resistance mechanisms to high vacuum, DNA-protective α/β-type small acid-soluble proteins, and non-homologous end joining and base excision repair of DNA played the most important roles, especially against multiple cycles of vacuum treatment. Overall, these results give new insight into individual spore's responses to space vacuum and provide new techniques for microorganism analysis at the single-cell level.
外层空间对所有生命形式来说都是一个充满挑战的环境，细菌的休眠孢子经常被用于研究陆地生命在太空旅行中的生存情况。先前的研究表明，仅外层空间真空就能杀死细菌孢子。然而，单个孢子对太空真空的反应和抗性机制尚不清楚。在此，我们使用显微拉曼光谱研究了在模拟太空真空（约10帕）下孢子的分子变化，发现这种真空不会导致孢子蛋白质发生显著变性。然后，我们开发了活细胞显微镜技术来研究单个孢子萌发、生长和繁殖过程中的实时事件。结果表明，在暴露于模拟太空真空10天后，两种孢子的活力降低了35%，但所有孢子仍保留了大量的钙吡啶二羧酸储备。一些死亡的孢子没有萌发，其余的萌发了但没有进入营养生长阶段。真空处理减缓了孢子的萌发，并改变了所有主要萌发事件的平均时间。此外，经过真空处理的存活孢子比未处理的孢子对干热和高渗胁迫表现出更高的敏感性。在孢子对高真空的抗性机制中，DNA保护型α/β型小酸溶性蛋白以及DNA的非同源末端连接和碱基切除修复发挥了最重要的作用，尤其是在应对多个周期的真空处理时。总体而言，这些结果为单个孢子对太空真空的反应提供了新的见解，并为单细胞水平的微生物分析提供了新技术。
