Asgard archaea

Asgard archaea are a group of archaeal lineages that includes the closest known prokaryotic relatives of eukaryotes. Several are named after figures and places in Norse mythology.

Archaea: Archaea are single-celled organisms distinct from bacteria and eukaryotes, with their own evolutionary history and molecular features. Asgard archaea are a group within this domain of life.
Eukaryogenesis: Eukaryogenesis is the evolutionary emergence of eukaryotic cells from their prokaryotic ancestors. Asgard genomes bear on which prokaryotic lineage contributed the host cell.
Loki’s Castle hydrothermal vent field: Loki’s Castle is a hydrothermal vent field on the Arctic Mid-Atlantic Ridge. Sediments near the vent yielded the genetic material used to identify Lokiarchaeota.
Two-domain system: The two-domain system groups life into Bacteria and Archaea, with eukaryotes arising from within Archaea. It places eukaryotes inside the archaeal tree rather than as a separate primary domain.
Eukaryote: A eukaryote is an organism whose cells contain a nucleus and other membrane-bound compartments. Eukaryotes are the branch of life most closely related to Asgard archaea.
Lokiarchaeota: Lokiarchaeota is an Asgard archaeal lineage first identified from environmental genetic material near Loki’s Castle hydrothermal vent. Its initial discovery brought attention to Asgard archaea as close eukaryotic relatives.
Metagenomics: Metagenomics analyzes genetic material recovered directly from environmental samples rather than from isolated organisms. Most Asgard lineages were first recognized through environmental DNA and reconstructed genomes.
Three-domain system: The three-domain system divides life into Bacteria, Archaea, and Eukarya as three primary evolutionary domains. It represents the older classification in which eukaryotes and archaea are separate domains.
Archaeal membrane: An archaeal membrane contains lipids with ether-linked chains attached to glycerol, unlike the usual ester-linked lipids of bacteria and eukaryotes. Their distinctive membranes help distinguish Asgard cells from their eukaryotic relatives.
Eukaryotic signature proteins: Eukaryotic signature proteins are protein families associated with cellular systems characteristic of eukaryotes. Asgard genomes encode homologues involved in processes such as membrane remodeling and cytoskeletal dynamics.

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