Resolving the ecological biodiversity of Asgard archaea and their role in the evolution of eukaryotes

导致所有植物、动物和真菌（即真核生物）所特有的含有膜结合细胞器的复杂细胞生命起源的过程仍然是一个谜。证据支持不同微生物谱系的细胞（古细菌和细菌）合并形成第一个真核细胞的情景。最近，被统称为“阿斯加德”微生物的新生命谱系的基因组被发现。令人惊讶的是，将这些生物添加到生命树中，揭示了它们与真核生物的密切关系，表明它们在真核生物的起源中发挥了重要作用。这些基因组的特征已经检测到以前只在更复杂的细胞生命中看到的基因。由于目前没有一种Asgard微生物可以在实验室中生长，因此该项目将利用高通量测序技术从深海沉积物中有针对性地发现这些微生物。这些数据将产生一个更全面的阿斯加德基因组目录，并将用于推断他们的生理能力，并了解他们祖先的基因组成。这项研究将为深海海底热液群落中Asgard微生物的生物多样性和代谢提供新的见解，并将为复杂真核生物的起源提供基础见解。该项目将为本科生和研究生提供研究培训，并将通过南德克萨斯科学和德克萨斯州科学中心的公共讲座向公众推广。最近，从几种缺氧环境中获得了新的古细菌超门“Asgard”的基因组（Heimdallarchaeota, Thorarchaeota， Odinarchaeota和Lokiarchaeota门）。令人惊讶的是，系统基因组学分析显示阿斯加德与真核生物密切相关，这表明这些生物是祖先古细菌宿主的后代。这些Asgard门含有多种编码真核特征蛋白（ESPs）的基因。ESPs与真核蛋白相似，参与细胞骨架形成、囊泡运输、蛋白质易位和糖基化等多种过程，这表明古细菌是真核细胞的一些细胞复杂性的起源。由于目前可用的Asgard基因组很少，因此该项目旨在对深海沉积物进行额外的高通量测序和基因组重建，以获得更全面的Asgard超门基因组目录。这些额外的基因组将用于更好地解决这些古细菌与真核生物的系统发育关系。研究人员还将对所有ESPs进行编目，以更好地解决它们在细胞复杂性起源中的作用。最后，该项目将解决这些古菌的生理能力，并模拟阿斯加德的祖先状态。这将促进我们对古细菌和真核生物最后共同祖先的生理能力的理解。确定这些古细菌的现代和远古生理状态将改变我们对真核生物起源的理解。

The processes that led to the origin of complex cellular life containing membrane-bound organelles, characteristic of all plants, animals and fungi, (i.e., eukaryotes) is still a mystery. Evidence supports the scenario where cells of different microbial lineages (archea and bacteria) merged to form the first eukaryotic cell. Recently, genomes belonging to new lineages of life, collectively called "Asgard" microorganisms, have been discovered. Surprisingly, the addition of these organisms to the tree of life have revealed a close relationship to eukaryotes, suggesting they played important roles in the origin of eukaryotes. Characterization of these genomes has detected genes previously only seen in more complex cellular life. Because currently none of the Asgard microorganism can be grown in the laboratory, this project will harness high-throughput sequencing techniques for a targeted discovery of these microorganisms from deep-sea sediments. These data will result in a more comprehensive catalog of Asgard genomes, and will be used to infer their physiological capabilities and to understand the genetic composition of their ancestor. This research will provide new insights into the biodiversity and metabolisms of Asgard microbes in deep ocean floor hydrothermal communities, and will add fundamental insights into the origin of complex eukaryotic life. This project will provide research training for undergraduate and graduate students, and will include outreach to the general public via the South Texas Science and public lectures at sciene centers in Texas. Recently, genomes (Heimdallarchaeota, Thorarchaeota, Odinarchaeota, and Lokiarchaeota phyla) belonging to the novel archaeal superphylum "Asgard" have been obtained from several anoxic environments. Surprisingly, phylogenomic analyses revealed Asgard is closely related to eukaryotes, suggesting that these organisms are descendants of the ancestral archaeal host. These Asgard phyla contain a variety of genes that encode for eukaryotic signature proteins (ESPs). ESPs are similar to eukaryotic proteins involved in a variety of processes including cytoskeletal formation, vesicular trafficking, protein translocation, and glycosylation, suggesting that archaea are the origin of some of the cellular complexity of eukaryotic cells. Because only few Asgard genomes are currently available, this project aims to do additional high-throughput sequencing and reconstruction of genomes from deep-sea sediments to obtain a more comprehensive genomic catalog of the Asgard superphylum. These additional genomes will be used to better resolve the phylogenetic relatedness of these archaea to eukaryotes. Researchers will also catalog the full repertoire of ESPs to better resolve their roles in the origin of cellular complexity. Finally, this project will resolve the physiological capabilities of these archaea and model the ancestral state of the Asgards. This will advance our understanding of the physiological capabilities of the last common ancestor of archaea and eukaryotes. Determining the modern and ancestral physiological states of these archaea will transform our understanding of the origin of eukaryotes.