近日，华东师范大学教授董宏坡及其小组报道了Asgardarchaeota内Heimdallarchaeia外真核生物的深层起源。相关论文发表在2025年5月7日出版的《自然》杂志上。

在这里，该研究组产生了223个宏基因组组装的几乎完整的阿斯加德古菌基因组，这些基因组以前没有被记录过。课题组人员确定了16个属级或更高级别的新谱系，这大大扩展了已知的阿斯加德古菌的系统发育多样性。通过对扩展的基因组数据集进行复杂的系统基因组学分析，包括几个标记集，小组推断真核生物在所有样本的Heimdallarchaeia多样化之前进化，而不是在Heimdallarchaeia中与Hodarchaeales分支。真核生物位置的差异可能是由以前未被重视的Njordarchaeales基因组的嵌合性质引起的，该研究组发现Njordarchaeales基因组由Asgard和TACK古细菌（Asgard的姐妹门）的序列组成。通过祖先重建和分子定年，该团队推断阿斯加德最后的古细菌和真核生物共同祖先出现在大氧化事件之前，可能是一种厌氧H₂依赖的醋酸菌。他们的发现支持真核发生的氢假说，该假说认为真核生物是由消耗H₂的古细菌宿主和产生H₂的原线粒体的离子产生的。

研究人员表示，对阿斯加德古菌的形态学、生理学和基因组学的研究为真核生物的进化史提供了宝贵的见解。先前的一项研究表明，真核生物嵌套在Hodarchaeales中，但它们在Asgard古细菌中的确切系统发育位置仍有争议。这一争论使对早期真核生物祖先的代谢特征和时间尺度的理解复杂化。

附：英文原文

Title: Deep origin of eukaryotes outside Heimdallarchaeia within Asgardarchaeota

Author: Zhang, Jiawei, Feng, Xiaoyuan, Li, Meng, Liu, Yang, Liu, Min, Hou, Li-Jun, Dong, Hong-Po

Issue&Volume: 2025-05-07

Abstract: Research on the morphology, physiology and genomics of Asgard archaea has provided valuable insights into the evolutionary history of eukaryotes1,2,3. A previous study suggested that eukaryotes are nested within Heimdallarchaeia4, but their exact phylogenetic placement within Asgard archaea remains controversial4,5. This debate complicates understanding of the metabolic features and timescales of early eukaryotic ancestors. Here we generated 223 metagenome-assembled nearly complete genomes of Asgard archaea that have not previously been documented. We identify 16 new lineages at the genus level or higher, which substantially expands the known phylogenetic diversity of Asgard archaea. Through sophisticated phylogenomic analysis of this expanded genomic dataset involving several marker sets we infer that eukaryotes evolved before the diversification of all sampled Heimdallarchaeia, rather than branching with Hodarchaeales within the Heimdallarchaeia. This difference in the placement of eukaryotes is probably caused by the previously underappreciated chimeric nature of Njordarchaeales genomes, which we find are composed of sequences of both Asgard and TACK archaea (Asgard’s sister phylum). Using ancestral reconstruction and molecular dating, we infer that the last Asgard archaea and eukaryote common ancestor emerged before the Great Oxidation Event and was probably an anaerobic H2-dependent acetogen. Our findings support the hydrogen hypothesis of eukaryogenesis, which posits that eukaryotes arose from the fusion of a H2-consuming archaeal host and a H2-producing protomitochondrion.

DOI: 10.1038/s41586-025-08955-7

Source: https://www.nature.com/articles/s41586-025-08955-7