History of the Hadean “Living Microfossil” OD1 and Ultra-reducing Environments
History of the Hadean “Living Microfossil” OD1 and Ultra-reducing Environments
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DOI：
10.5026/jgeography.128.571
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发表时间：
2019-08
期刊：
影响因子：
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通讯作者：
Tomohiko Sato;Kazumi Yoshiya;S. Maruyama
中科院分区：
文献类型：
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作者：
Tomohiko Sato;Kazumi Yoshiya;S. Maruyama
系统发育分析是揭示地球上生命进化的有用工具之一，但仅仅通过比较系统发育树来区分新旧基因组在原则上是困难的。为了克服这一困难，引入了一种新的方法，即利用来自地质信息的地球历史来追踪基因组进化。这个想法的灵感来自达尔文的自然选择，并解释了生物是如何随着环境的变化而变化的。换句话说，如果环境保持不变，生命的基因组就不会改变。一个关键是Hadean地球上生命的诞生地，那里被认为是一个超还原的环境，通过蛇纹岩作用产生大量的H2。OD1是一种潜在的微生物，自Hadean以来一直存活在地球上。它的栖息地，日本的Hakuba-Happo，是陆地上独特的蛇纹岩赋存的热液系统，从Hadean到现在，它一直保持在超还原环境中，从而避免了进化。OD1被认为是Hadean微生物的“活化石”。在地球历史上，超还原环境已经消失了。从Hadean时代到现在，OD1是如何生存下来的？基于板块构造，提出了一种可能的情景。OD1栖息地经历了以下转变：(1)原始大陆上天然核间歇泉的超还原环境；(2)太古代-元古界沿大洋中脊转换断层的蛇纹岩容矿热液系统；(3)俯冲-吸积和从氧化显生体洋底逃逸；(4)由于增生杂岩的生长和火山前缘上方的热液系统而向上抬升。OD1栖息地随着地质时代的推移而减少，因为地表环境中的游离氧增加了。OD1可能是哈迪亚的一块“活的微化石”，它依靠钢丝在超还原环境中不断前进。
Phylogenetic analysis is one of the useful tools available for revealing the evolution of life on the Earth; however, it has difficulty in principle distinguishing old and new genomes just by comparing phylogenomic trees. To overcome this difficulty, a new method is introduced which utilizes the Earth’s history derived from geologic information to trace genomic evolution. This idea is inspired by Darwin’s natural selection, and explains how living organisms change with the environment. In other words, life’s genome does not change if the environment remains the same. A key is the birthplace of life on Hadean Earth, which is thought to be an ultra-reducing environment with H2 produced in abundance through serpentinization. OD1 is a potential microbe that has survived on the Earth since the Hadean. Its habitat, Hakuba-Happo in Japan, is a unique serpentinite-hosted hydrothermal system on land, and it has avoided evolution by remaining in a super-reducing environment from the Hadean to the present. OD1 is regarded as a “living fossil” of the Hadean microbe. Ultra-reducing environments have disappeared over the Earth’s history. How has OD1 survived since the Hadean to the present? A possible scenario is proposed based on Plate Tectonics. OD1 habitats have gone through the following transitions: (1) super-reducing environment in a natural nuclear geyser on a primordial continent in the Hadean; (2) serpentinite-hosted hydrothermal system along a mid-oceanic ridge transform fault during the Archean-Proterozoic; (3) subduction-accretion and escape from oxygenated Phanerozoic ocean floor; and, (4) jacked up by growth of accretionary complexes and taking refuge in a hydrothermal system above a volcanic front. OD1 habitats have been reduced with geological age as free oxygen has increased in the surface environment. OD1 may be a “living microfossil” of the Hadean, making its way continuously through ultra-reducing environments on a tightrope.