Archaea and the origin of eukaryotes

• Published in: Nature reviews. Microbiology Vol. 15; no. 12; pp. 711 - 723
• Main Authors: Eme, Laura, Spang, Anja, Lombard, Jonathan, Stairs, Courtney W., Ettema, Thijs J. G.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.12.2017; Nature Publishing Group
• Subjects: 631/181/2468; 631/208/182; 631/208/2156; 631/208/464; 631/326/26/2142; 631/326/26/2523; 631/326/26/2524; 631/326/26/2526; 631/326/26/2527; Analysis; Archaea; Archaea - genetics; Bacteria; Biological Evolution; Biological research; Eukaryota - genetics; Eukaryotes; Evolution; Evolutionary biology; Genetic aspects; Infectious Diseases; Life Sciences; Medical Microbiology; Microbiology; Mitochondria; Parasitology; Pharmacogenomic Variants; Phylogeny; Prokaryotes; review-article; Virology
• ISSN: 1740-1526; 1740-1534; 1740-1534
• DOI: 10.1038/nrmicro.2017.133

Key Points The Archaea was recognized as a third domain of life 40 years ago. Molecular evidence soon suggested that the Eukarya represented a sister group to the Archaea or that eukaryotes descended from archaea. Culture-independent genomics has revealed the vast diversity existing among the Archaea, including the recently described Asgard superphylum. Phylogenomic analyses have placed the Asgard archaea as the closest prokaryotic relatives of eukaryotes. Comparative genomic analyses have reconstructed a complex last eukaryotic common ancestor. However, how and in which order these complex eukaryotic features evolved in an Asgard archaea-related ancestor remains largely unclear. Genomic investigation of Asgard archaea showed that they carry several genes formerly believed to be eukaryotic specific, illuminating early events during eukaryogenesis. Fully understanding the process of eukaryogenesis requires finding answers to several challenging and intertwined questions. Although we have seemingly answered some of these questions, others remain fiercely debated, and new questions continue to arise. The Archaea was recognized as a third domain of life 40 years ago. In this Review, Eme et al . outline a brief history of the changing shape of the tree of life and examine how the recent discovery of diverse archaeal lineages has changed our understanding of the evolutionary relationships between the three domains of life and the origin of the eukaryotic cell. Woese and Fox's 1977 paper on the discovery of the Archaea triggered a revolution in the field of evolutionary biology by showing that life was divided into not only prokaryotes and eukaryotes. Rather, they revealed that prokaryotes comprise two distinct types of organisms, the Bacteria and the Archaea. In subsequent years, molecular phylogenetic analyses indicated that eukaryotes and the Archaea represent sister groups in the tree of life. During the genomic era, it became evident that eukaryotic cells possess a mixture of archaeal and bacterial features in addition to eukaryotic-specific features. Although it has been generally accepted for some time that mitochondria descend from endosymbiotic alphaproteobacteria, the precise evolutionary relationship between eukaryotes and archaea has continued to be a subject of debate. In this Review, we outline a brief history of the changing shape of the tree of life and examine how the recent discovery of a myriad of diverse archaeal lineages has changed our understanding of the evolutionary relationships between the three domains of life and the origin of eukaryotes. Furthermore, we revisit central questions regarding the process of eukaryogenesis and discuss what can currently be inferred about the evolutionary transition from the first to the last eukaryotic common ancestor.