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.
