archaeaeukaryotes

The term archaeaeukaryotes refers to the proposed clade that groups archaea and eukaryotes as closely related lineages within a common evolutionary framework. In some literature it is used to describe the conceptual unity of Archaea and Eukarya, highlighting their genetic affinities.

In traditional taxonomy life has been divided into three domains: Bacteria, Archaea, and Eukarya. In a two-domain model, eukaryotes are thought to have emerged from within Archaea, making Archaea and Eukarya a single larger clade. The term archaeaeukaryotes is not a universally accepted formal taxon but a descriptive label for this relationship.

Support comes from comparative genomics and the discovery of Asgard archaea (Lokiarchaeota, etc.) which possess numerous eukaryotic signature proteins involved in cytoskeletal formation, membrane trafficking, and ubiquitin systems. These parallels suggest a close archaeal ancestor of eukaryotes.

Eukaryogenesis is believed to involve an archaeal host acquiring endosymbiotic bacteria that became mitochondria, followed by further cellular innovations such as the nucleus and complex endomembrane systems. This endosymbiotic event is central to the emergence of eukaryotes within the archaeaeukaryote framework.

Consequently, archaeaeukaryotes would exhibit a mosaic genome combining archaeal transcription and replication machinery with eukaryotic-like cellular features and gene families. They do not constitute a formal taxon in all classifications.

The concept remains debated, and ongoing genomic and phylogenetic studies refine the boundaries and composition of the archaeaeukaryote group, with Asgard archaeal lineages being a focal area of research.