西亚试剂：Complex archaea that bridge the gap between prokaryotes and

The origin of the eukaryotic cell remains one of the most contentious puzzles in modern biology. Recent studies have provided support for the emergence of the eukaryotic host cell from within the archaeal domain of life, but the identity and nature of the putative archaeal ancestor remain a subject of debate. Here we describe the discovery of ‘Lokiarchaeota’, a novel candidate archaeal phylum, which forms a monophyletic group with eukaryotes in phylogenomic analyses, and whose genomes encode an expanded repertoire of eukaryotic signature proteins that are suggestive of sophisticated membrane remodelling capabilities. Our results provide strong support for hypotheses in which the eukaryotic host evolved from a bona fide archaeon, and demonstrate that many components that underpin eukaryote-specific features were already present in that ancestor. This provided the host with a rich genomic ‘starter-kit’ to support the increase in the cellular and genomic complexity that is characteristic of eukaryotes.

真核细胞与原核生物的差别是如此之大，以至于了解真核生物起源和祖先一直是一个谜。遗传研究表明，古生菌比细菌更接近真核生物，但从生物化学上和形态上来说，古生菌与细菌的关系比与真核生物更近。但是现在，Thijs Ettema及同事从来自 “Loki’s Castle”活动热液喷发点的一个岩芯样本识别出了一些古生菌，它们符合作为一个基因组 “starter-kit”的要求，能够支持作为真核生物特征的更大的细胞和基因组复杂性。被称为Lokiarchaeota的这一新的古生菌类群在系统发生分析中是真核生物一个最相近的姐妹类群，它们所拥有的蛋白质本应是真核生物的特征。

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