Archaea and the origin of eukaryotes

Abstract

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.

Why the Lipid Divide? Membrane Proteins as Drivers of the Split between the Lipids of the Three Domains of Life

“…Such a scenario would allow for a eukaryotic ancestor that, from the start, brought with it traits that we now associate with the archaea and the bacteria, including an archaeal‐like information machinery but bacterial‐like membrane lipids. This view is not without supporters, but even allowing for a later mitochondrial endosymbiosis it would seem to be at odds with much of the evidence amassed in recent years …”

“…This view is not without supporters, [3] but even allowing for a later mitochondrial endosymbiosis it would seem to be at odds with much of the evidence amassed in recent years. [7,8,11]…”

“…The core topology of the tree of life remains contentious, [2][3][4] but evidence amassed over the last decade supports the view that eukaryotes as we presently know them arose from a merger of prokaryotic cells, [5][6][7][8][9] involving an archaeal host [10][11][12] (likely from within the recently described Asgard superphylum) [13,14] and an endosymbiotic [5] bacterium (likely from a lineage within or closely related to the modern Alphaproteobacteria). [15][16][17] If this was the case, eukaryotes likely inherited their membrane lipids from their prokaryotic forebears.…”

No genome is an island: toward a 21st century agenda for evolution

“…The ancestor of all eukaryotic cells, in contrast, arose less than 1.8 GYA following an endosymbiogenetic merger of an aerobic proteobacterium and an unknown but advanced archaeal cell . This conclusion is based on two kinds of observations: DNA evidence shows that all known eukaryotes, with a single exception, carry mitochondria or mitochondrion‐derived organelles .…”

Entities inside one another ‐ a matryoshka doll in biology?

“…It is theorized that symbiogenesis (endosymbiont theory) was a prominent event in the evolution of the eukaryotic cell through the acquisition of an alphaproteobacterium by a proto-eukaryote, leading to the evolution of the endosymbiont mitochondria (Zimorski et al, 2014;Archibald, 2015;Martin et al, 2015;Roger et al, 2017;Eme et al, 2018). Later on in a mitochondrion-containing eukaryote, cyanobacteria were engulfed and evolved to form chloroplasts (Archibald, 2015;Martin et al, 2015).…”