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An important step in the evolution of plants, animals, and other complex, multicellular forms of life was eukaryogenesis, the evolution of eukaryotes. Eukaryotes are one of the three major classifications of life (alongside single-celled bacteria and archaea) and are characterized by cellular compartmentalization, an extensive membrane network inside of the cells, and the presence of mitochondria. A lot of recent work has focused on refining the origins of eukaryotes, which are thought to have evolved from the fusion between an archaeon and a bacterium (which became the mitochondria). Recent work has narrowed down the origin of our archaeal ancestor to among a newly discovered group of archaea dubbed the Asgard superphylum.
Scientists have also been working toward pinning down the https://www.physicsforums.com/insights/when-did-origin of our mitochondria. Because scientists had thought mitochondria evolved from a group of bacteria known as the alphaproteobacteria (specifically a bacterium closely related to the present day Rickettsiales group), a research team led by Thijs Ettema (the scientist who discovered the Asgard archaea described above) set out to collect a diverse set of alphaproteobacteria from across the world to narrow down the origins of mitochondria. Instead of finding a close relative of the mitochondria, however, they instead found something even more surprising:
A wider sampling of alphaproteobacteria and improved techniques for analyzing DNA sequences seemed to suggest that our previous hypotheses about the origin of mitochondria were wrong. Instead of residing within alphaproteobacteria, the ancestor of the mitochondria may have been part of a more distantly related group of bacteria that remains to be defined. Discovering the exact origins of the mitochondria (and even identifying extant relatives of that ancestor) will be an exciting challenge for the researchers going forward.
Citation to the study discussed:
Martijn et al. (2018) Deep mitochondrial origin outside the sampled alphaproteobacteria. Nature Published online 25 April 2018
http://dx.doi.org/10.1038/s41586-018-0059-5
Scientists have also been working toward pinning down the https://www.physicsforums.com/insights/when-did-origin of our mitochondria. Because scientists had thought mitochondria evolved from a group of bacteria known as the alphaproteobacteria (specifically a bacterium closely related to the present day Rickettsiales group), a research team led by Thijs Ettema (the scientist who discovered the Asgard archaea described above) set out to collect a diverse set of alphaproteobacteria from across the world to narrow down the origins of mitochondria. Instead of finding a close relative of the mitochondria, however, they instead found something even more surprising:
https://www.the-scientist.com/?arti...tle/Mitochondria-s-Bacterial-Origins-Upended/
A wider sampling of alphaproteobacteria and improved techniques for analyzing DNA sequences seemed to suggest that our previous hypotheses about the origin of mitochondria were wrong. Instead of residing within alphaproteobacteria, the ancestor of the mitochondria may have been part of a more distantly related group of bacteria that remains to be defined. Discovering the exact origins of the mitochondria (and even identifying extant relatives of that ancestor) will be an exciting challenge for the researchers going forward.
Citation to the study discussed:
Martijn et al. (2018) Deep mitochondrial origin outside the sampled alphaproteobacteria. Nature Published online 25 April 2018
http://dx.doi.org/10.1038/s41586-018-0059-5
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