Symbiogenesis
From The Art and Popular Culture Encyclopedia
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Symbiogenesis, or endosymbiotic theory, is an evolutionary theory of the origin of eukaryotic cells from prokaryotic organisms, first articulated in 1905 and 1910 by the Russian botanist Konstantin Mereschkowski, and advanced and substantiated with microbiological evidence by Lynn Margulis in 1967. It holds that the organelles distinguishing eukaryote cells evolved through symbiosis of individual single-celled prokaryotes (bacteria and archaea). The theory holds that mitochondria, plastids such as chloroplasts, and possibly other organelles of eukaryotic cells represent formerly free-living prokaryotes taken one inside the other in endosymbiosis. In more detail, mitochondria appear to be related to Rickettsiales proteobacteria, and chloroplasts to nitrogen-fixing filamentous cyanobacteria. Among the many lines of evidence supporting symbiogenesis are that new mitochondria and plastids are formed only through binary fission, and that cells cannot create new ones otherwise; that the transport proteins called porins are found in the outer membranes of mitochondria, chloroplasts and bacterial cell membranes; that cardiolipin is found only in the inner mitochondrial membrane and bacterial cell membranes; and that some mitochondria and plastids contain single circular DNA molecules similar to the chromosomes of bacteria.
See also
- Angomonas deanei, a protozoan that harbours an obligate bacterial symbiont
- Hatena arenicola, a species that appears to be in the process of acquiring an endosymbiont
- Hydrogen hypothesis
- James A. Lake
- Kleptoplasty
- Mixotricha paradoxa, which itself is a symbiont, contains endosymbiotic bacteria
- Numt, abbreviation of "nuclear mitochondrial DNA"
- Parasite Eve, fiction about endosymbiosis
- Protocell
- Viral eukaryogenesis, hypothesis that the cell nucleus originated from endosymbiosis
