The last 50 years, a variety of archaea and bacteria able to withstand extremely high doses of ionizing radiation, have been discovered. Several lines of evidence suggest a variety of mechanisms explaining the extreme radioresistance of microorganisms found usually in isolated environments on Earth. These findings are discussed thoroughly in this study. Although none of the strategies discussed here, appear to be universal against ionizing radiation, a general trend was found. There are two cellular mechanisms by which radioresistance is achieved: (a) protection of the proteome and DNA from damage induced by ionizing radiation and (b) recruitment of advanced and highly sophisticated DNA repair mechanisms, in order to reconstruct a fully functional genome. In this review, we critically discuss various protecting (antioxidant enzymes, presence or absence of certain elements, high metal ion or salt concentration etc.) and repair (Homologous Recombination, Single-Strand Annealing, Extended Synthesis-Dependent Strand Annealing) mechanisms that have been proposed to account for the extraordinary abilities of radioresistant organisms and the homologous radioresistance signature genes in these organisms. In addition, and based on structural comparative analysis of major radioresistant organisms, we suggest future directions and how humans could innately improve their resistance to radiation-induced toxicity, based on this knowledge.

中文翻译：

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揭示原核生物中极端抗辐射的机制：自然的教训。

在最近的50年中，已经发现了各种能够承受极高剂量电离辐射的古细菌和细菌。有几条证据表明，多种机制可以解释通常在地球上孤立的环境中发现的微生物的极强抗辐射性。这些发现在本研究中进行了详尽的讨论。尽管这里讨论的所有策略都没有针对电离辐射的通用方法，但已发现了总体趋势。可以通过两种细胞机制实现放射抗性：（a）保护蛋白质组和DNA免受电离辐射引起的损害，以及（b）募集先进且高度复杂的DNA修复机制，以重建功能齐全的基因组。在这篇评论中，我们将重点讨论各种保护（抗氧化酶，某些元素的存在或不存在，高金属离子或盐浓度等）和修复（同源重组，单链退火，扩展合成依赖链退火）机制已被提出来说明抗辐射生物体的非凡能力和这些生物体中的同源放射抗性签名基因。此外，基于对主要耐辐射生物的结构比较分析，我们基于此知识提出了未来的方向以及人类如何固有地提高其对辐射诱导的毒性的抵抗力。已提出扩展的依赖于合成的链退火机制，以解释辐射抗性生物体的超常能力以及这些生物体中的同源辐射抗性签名基因。此外，基于对主要耐辐射生物的结构比较分析，我们基于此知识提出了未来的方向以及人类如何固有地提高其对辐射诱导的毒性的抵抗力。已提出扩展的依赖于合成的链退火机制，以解释辐射抗性生物体的超常能力以及这些生物体中的同源辐射抗性签名基因。此外，基于对主要耐辐射生物的结构比较分析，我们基于此知识提出了未来的方向以及人类如何固有地提高其对辐射诱导的毒性的抵抗力。