|Chatton , 1925|
Eukaryotes or eukaryotes (Eukaryota) are a domain of living beings whose cells ( eucytes ) have a real nucleus and a rich compartmentalization ( animals , plants and fungi ). This is where they differ from the other two domains in the system of living beings , the prokaryotic bacteria and archaea (the latter also known as primordial bacteria in the past), both with procytic cells.
The cells of the eukaryotes usually have a diameter of 10 to 30 µm. They are usually much larger than those of prokaryotes , their volume is about 100 to 10,000 times. For a smooth functioning of the cellular processes over larger distances within the cell, a higher degree of organization and a division of the cell space into compartments (delimited spaces) as well as transport between these compartments are favorable. For this reason, eukaryotic cells are structured by means of cell organelles which, like the organs of a body, perform different functions. The organelle that gives it its name is the nucleus with most of the genetic material of the eukaryotic cells. Depending on the type, other genes are found in mitochondria (organelles that provide energy through chemical reactions), in individual cases also in their related hydrogenosomes and in almost all plastids (including the photosynthetic chloroplasts ). The organelles of the endomembrane system serve for intracellular transport .
Structure and shape are given to the eukaryotic cells by the cytoskeleton , which is also used for locomotion. It is made up of microtubules , intermediate filaments and microfilaments . Some eukaryotes, such as plants and fungi, also have cell walls that enclose the cells outside the cytoplasmic membrane and determine their shape.
Eukaryotes can be single-cell or multicellular organisms. These consist of a large number of cells with a common metabolism, with special cell types taking on certain tasks. Most of the known multicellular cells are eukaryotes, including plants , animals and multicellular fungi .
In the biological system , the eukaryotes form one of the three domains , i.e. the highest categories for the classification of living beings. The current systematics of the eukaryotes was developed by Adl et al. Established in 2012. It divides the eukaryotes as follows:
- super-group Excavata , unicellular organisms, the majority of which are flagellated
There are also numerous taxa with an uncertain position ( incertae sedis ), including among others
- Camera lens , a flagellate species and the only representative of the camera genus
System according to Cavalier-Smith
Cavalier-Smith classifies the eukaryotes as follows:
The oldest macroscopic, multicellular, possibly eukaryotic fossils are 1.5 billion years old. It is not known whether the hypothetical evolutionary precursors of the eukaryotes - the so-called original karyotes - already had organelles (these would have been necessary due to the disadvantageous surface-volume ratio) or whether they only acquired them in the course of their evolution towards the actual eukaryotes. The best-known theory about the origin of organelles is the endosymbiotic theory , which states that mitochondria and chloroplasts go back to bacteria that were originally ingested as food by the cell-biological "primitive", predatory karyotes and some of which were not digested by chance, but a symbiosis entered with the original karyote.
The last common ancestor of all today's eukaryotes - also called Last Eukaryotic Common Ancestor , LECA for short - should have had both a demarcated nucleus and mitochondria, since all eukaryotes examined so far have mitochondria, mitochondrial-like organelles or at least nuclear DNA of mitochondrial origin (transferred by lateral gene transfer ). Although Thomas Cavalier-Smith introduced the designation Archezoa for recent amitochondrial protozoa with a nucleus, which he considered to be evolutionary relics from the time before LECA, there was increasing evidence that the Archezoa are secondary amitochondrial real eukaryotes, that is, descendants of LECA.
As an alternative to the original karyote hypothesis, an acquisition of mitochondria by archaea is being discussed ( hydrogen hypothesis ) before or at the same time as the nucleus, which could possibly be of viral origin (among the NCLDVs ) ("viral eukaryogenesis", part of the " Out-of-Virus Hypothesis "). DNA viruses such as the ' Medusaviridae ' are traded as candidates; and also the ' Pseudomonas Phage 201phi2-1 ' from the genus Phikzvirus , family Myoviridae , a giant bacteriophage , forms a nucleus-like structure when a bacterial cell is infected, which separates proteins depending on their function, this nucleus-like structure and its key properties were also found in found the related phage.
A summary of this discussion can be found in Traci Watson (2019); on the different points of view see Guglielmini et al. (2019) and Koonin / Yutin (2018).
The formation of the chloroplasts of photosynthesizing eukaryotes by endosymbiosis is a later process. Initially, cyanobacteria were ingested by non-phototrophic eukaryotes, which possibly happened only once in this form ( primary endosymbiosis ). The other plastids ( leukoplasts etc.) are derived from these.
Later, complex plastids (with more than double membrane and possibly nucleosome ) developed through a secondary endosymbiosis , i.e. H. (Other) non-phototrophic eukaryotes took in phototrophic eukaryotes (resulting from the primary endosymbiosis) through endosymbiosis (for example with the Apicomplexa ).
This division initially faded into the background with the introduction of the three- domain system by Carl Woese in 1977, an approach that divides cellular life into the three domains of bacteria, archaea and eukaryotes.
In 1984, James A. Lake and colleagues proposed the eocyte hypothesis : It had been discovered that the shape of the ribosomes in the archaeal group of crenarchaeota (originally called eocytes) and eukaryotes was remarkably similar but the shape of the ribosomes both in bacteria and in the Euryarchaeota , another group of archaea, differs significantly from it. It was therefore assumed that the eukaryotes emerged from the Crenarchaeota.
Despite further evidence in the 1980s, the eocyte hypothesis only got a new impetus in the 2000s with the advancement of genome analysis. Genes that are found in a similar form in eukaryotes have been discovered in a number of archaea. According to the results of some studies, instead of the Crenarchaeota, the related group of Thaumarchaeota was proposed as the origin of the eukaryotes. (The Crenarchaeota and Thaumarchaeota are combined together with some other archaea groups in the supergroup "TACK").
With the advent of metagenomic analysis , since 2015, it has been possible to identify candidates for archaeal groups in samples from the vicinity of hydrothermal sources , which must be much closer to the eukaryotes than any of the groups previously considered. The first group was that of the " Lokiarchaeota ", found at a hydrothermal vent called " Loki 's Castle" in the Arctic Ocean between the poppy and Knipovich ridges . Since these findings only come from a metagenome analysis and the microbes in question cannot be cultivated for the time being, all taxa in question only have a 'candidate status', indicated by the quotation marks.
The "Lokiarchaeota" are combined into a candidate group " Asgard " due to their similarity in the genome with some groups recently proposed in this context (" Thorarchaeota ", " Odinarchaeota " and " Heimdallarchaeota ") , which among the archaea is the eukaryotes is next and represents a sister taxon to the supergroup "TACK".
In order to take account of the close relationship between the archaea and the eukaryotes, Thomas Cavalier-Smith placed them in a common taxon Neomura in 2002 , which is a sister group to the bacteria.
This new classification is supported by more recent findings, according to which the use of the DNA genome as the carrier of genetic information in bacteria on the one hand and archaea and eukaryotes on the other seems to have different (possibly viral: another part of the “out-of-virus hypothesis”) . The last common ancestor of all living things known today would have been an archaic cellular organism of the RNA world (with ribosomes , i.e. protein synthesis).
The theory gets further support by examining the structure of the membrane-bound F- and V- / A-type ATPases . The F-type ATPases of the mitochondria and chloroplasts are homologous with those of the bacteria (as expected according to the endosymbiosis theory ). The V-type ATPases on cytoplasmic membranes ( vacuoles ) of the eukaryotes are homologous to those of the archaea, which supports the ancestry of the eukaryotes from a branch of the archaea. Isolated exceptions (F-type ATPases in some archaea species and V-type ATPases in some bacterial groups) are attributed to horizontal gene transfer . Central subunits of the ATPases are homologous across all living beings, which speaks for a LUCA with an at least primitive membrane envelope.
- Eukaryotes. In: Lexicon of Biology . Spectrum Academic Publishing House. Heidelberg, 1999, accessed October 1, 2016 .
- Gerald Karp, Molecular Cell Biology , 2005, p. 25.
- Adl, SM, Simpson, AGB, Lane, CE, Lukeš, J., Bass, D., Bowser, SS, Brown, MW, Burki, F., Dunthorn, M., Hampl, V., Heiss, A. , Hoppenrath, M., Lara, E., le Gall, L., Lynn, DH, McManus, H., Mitchell, EAD, Mozley-Stanridge, SE, Parfrey, LW, Pawlowski, J., Rueckert, S., Shadwick, L., Schoch, CL, Smirnov, A. and Spiegel, FW: The Revised Classification of Eukaryotes. Journal of Eukaryotic Microbiology , 59: pp. 429-514, 2012, doi : 10.1111 / j.1550-7408.2012.00644.x (PDF)
- Romain Derelle, Guifré Torruella, Vladimír Klimeš, Henner Brinkmann, Eunsoo Kim, Čestmír Vlček, B. Franz Lang, Marek Eliáš: Bacterial proteins pinpoint a single eukaryotic root . In: Proceedings of the National Academy of Sciences . 112, No. 7, February 17, 2015, , pp. E693-E699. doi : 10.1073 / pnas.1420657112 . PMID 25646484 . PMC 4343179 (free full text).
- T. Cavalier-Smith, EE Chao, EA Snell, C. Berney, AM Fiore-Donno, R. Lewis: Multigene eukaryote phylogeny reveals the likely protozoan ancestors of opisthokonts (animals, fungi, choanozoans) and Amoebozoa . In: Molecular Phylogenetics & Evolution . 81, 2014, pp. 71-85. doi : 10.1016 / j.ympev.2014.08.012 .
- Thomas Cavalier-Smith: Kingdoms Protozoa and Chromista and the eozoan root of the eukaryotic tree . In: Biology Letters . 6, No. 3, June 23, 2010, , pp. 342-345. doi : 10.1098 / rsbl.2009.0948 . PMID 20031978 . PMC 2880060 (free full text).
- Ding He, Omar Fiz-Palacios, Cheng-Jie Fu, Johanna Fehling, Chun-Chieh Tsai, Sandra L. Baldauf: An Alternative Root for the Eukaryote Tree of Life . In: Current Biology . 24, No. 4, August, pp. 465-470. doi : 10.1016 / j.cub.2014.01.036 .
- Laura A. Hug, Brett J. Baker, Karthik Anantharaman, Christopher T. Brown, Alexander J. Probst, Cindy J. Castelle, Cristina N. Butterfield, Alex W. Hernsdorf, Yuki Amano: A new view of the tree of life . In: Nature Microbiology . 1, No. 5, April 11, 2016, . doi : 10.1038 / nmicrobiol.2016.48 .
- Thomas Cavalier-Smith: Kingdom Chromista and its eight phyla: a new synthesis emphasizing periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences . In: Protoplasm . September 5, 2017, doi : 10.1007 / s00709-017-1147-3 . , pp. 1-61.
- Thomas Cavalier-Smith: Euglenoid pellicle morphogenesis and evolution in light of comparative ultrastructure and trypanosomatid biology: semi-conservative microtubule / strip duplication, strip shaping and transformation . In: European Journal of Protistology . August. doi : 10.1016 / j.ejop.2017.09.002 .
- Eugene V. Koonin: Energetics and population genetics at the root of eukaryotic cellular and genomic complexity . In: Proceedings of the National Academy of Sciences . 112, No. 52, pp. 15777-15778. doi : 10.1073 / pnas.1520869112 .
- Eukaryotes: A New Timeline of Evolution. Newsroom, Max Planck Society, May 24, 2015.
- CR Woese, GE Fox: Phylogenetic structure of the prokaryotic domain: the primary kingdoms. In: Proceedings of the National Academy of Sciences . Volume 74, Number 11, November 1977, pp. 5088-5090, PMID 270744 , PMC 432104 (free full text).
- Lynn Margulis, Dorion Sagan: Life: From Origin to Diversity . Spektrum Akademischer Verlag, Heidelberg, Berlin 1997, ISBN 3-8274-0524-6 (translation of the English-language original edition from 1995).
- Lynn Margulis: The Other Evolution . Spektrum Akademischer Verlag, Heidelberg, Berlin 1999, ISBN 3-8274-0294-8 (translation of the English-language original edition from 1998).
- Eugene V. Koonin: The origin and early evolution of eukaryotes in the light of phylogenomics , in: Genome Biology. Volume 11, item no. 209, May 5, 2010, doi: 10.1186 / gb-2010-11-5-209 .
- Tom Cavalier-Smith: Archaebacteria and Archezoa . In: Nature . 339, No. 6220, May 1989, pp. 100-101. doi : 10.1038 / 339100a0 . PMID 2497352 .
- Patrick J. Keeling: A kingdom's progress: Archezoa and the origin of eukaryotes. In: BioEssays. Volume 20, number 1, January 1998, pp. 87–95, doi : 10.1002 / (SICI) 1521-1878 (199801) 20: 1 <87 :: AID-BIES12> 3.0.CO; 2-4 (alternative full text access : SemanticScholar ).
- Martin W and Müller M: The hydrogen hypothesis for the first eukaryote . In: Nature . 392, No. 6671, 1998, pp. 37-41. doi : 10.1038 / 32096 . PMID 9510246 .
- Patrick Forterre: Evolution - The true nature of viruses , in: Spectrum August 2017, p. 37 (online article from July 19, 2017)
- Tokyo University of Science : New giant virus may help scientists better understand the emergence of complex life - Large DNA virus that helps scientists understand the origins of DNA replication and the evolution of complex life . In: EurekAlert! , April 30, 2019. Retrieved July 2, 2019.
- Pseudomonas phage 201phi2-1 , on: Virus-Host DB, TAX: 198110
- Proteomes - Pseudomonas phage 201phi2-1 , on: UniProt
- V Chaikeeratisak, K Nguyen, K Khanna, AF Brilot, ML Erb, JKC Coker, A Vavilina, GL Newton, R Busch Auer, K Pogliano, E Villa, DA Agard, J Pogliano: assembly of a nucleus-like structure during viral replication in bacteria . In: Science . 355, No. 6321, 2017, pp. 194–197. bibcode : 2017Sci ... 355..194C . doi : 10.1126 / science.aal2130 . PMID 28082593 . PMC 6028185 (free full text).
- V Chaikeeratisak, K Nguyen, ME Egan, ML Erb, A Vavilina, J Pogliano: The phage Nucleus and tubulin Spindle Are Conserved among Large Pseudomonas Phages . In: Cell Reports . 20, No. 7, 2017, pp. 1563–1571. doi : 10.1016 / j.celrep.2017.07.064 . PMID 28813669 . PMC 6028189 (free full text).
- Traci Watson: The trickster microbes that are shaking up the tree of life , in: Nature from May 14, 2019 (English), Trickser bacteria shake the family tree of life , in: Spektrum.de from June 20, 2019 (German) - the term 'bacteria' is not entirely correct; the microbes considered are archaea or (according to some researchers) at least proto- eukaryotes different from bacteria .
- Julien Guglielmini, Anthony C. Woo, Mart Krupovic, Patrick Forterre, Morgan Gaia: Diversification of giant and large eukaryotic dsDNnA viruses predated the origin of modern eukaryotes , in: PNAS 116 (39), 10./24. September 2019, pp. 19585-19592, doi: 10.1073 / pnas.1912006116 , PMID 31506349 , Fig. 2
- Julien Guglielmini, Anthony Woo, Mart Krupovic, Patrick Forterre, Morgan Gaia: Diversification of giant and large eukaryotic dsDNA viruses predated the origin of modern eukaryotes , on: bioRxiv of October 29, 2018, bioRxiv : 10.1101 / 455816v1 ( Preprint - full text) , doi: 10.1101 / 455816
- Eugene V. Koonin, Natalya Yutin: Multiple evolutionary origins of giant viruses , in: F1000 Research, November 22, 2018, doi: 10.12688 / f1000research.16248.1 , version 1
- Ralph, S .: Evolutionary Pressures on Apicoplast Transit Peptides . In: Molecular Biology and Evolution . 21, No. 12, 2004, pp. 2183-2191. doi : 10.1093 / molbev / msh233 . PMID 15317876 . ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.
- Edouard Chatton: Pansporella perplexa. Reflections on the biology and the phylogénie des protozoaires. In: Annales des Sciences Naturelles: Zoologie Sér. 10, Vol. 8, 1925, pp. 5-84.
- Marie-Odile Soyer-Gobillard: Edouard Chatton (1883-1947) and the dinoflagellate protists: concepts and models. In: International Microbiology. Volume 9, 2006, pp. 173-177. (pdf)
- Woese C, Fox G: Phylogenetic structure of the bacteria domain: the primary kingdoms . In: Proc Natl Acad Sci USA . 74, No. 11, 1977, pp. 5088-90. bibcode : 1977PNAS ... 74.5088W . doi : 10.1073 / pnas.74.11.5088 . PMID 270744 . PMC 432104 (free full text).
- Woese C, Kandler O, Wheelis M: Towards a natural system of organisms: proposal for the domains Archaea, Bacteria, and Eucarya. . In: Proc Natl Acad Sci USA . 87, No. 12, 1990, pp. 4576-9. bibcode : 1990PNAS ... 87.4576W . doi : 10.1073 / pnas.87.12.4576 . PMID 2112744 . PMC 54159 (free full text). Retrieved February 11, 2010.
- John M. Archibald: The eocyte hypothesis and the origin of eukaryotic cells . In: PNAS . 105, No. 51, December 23, 2008, pp. 20049-20050. doi : 10.1073 / pnas.0811118106 . Retrieved October 5, 2012.
- James A. Lake, Eric Henderson, Melanie Oakes, Michael W. Clark: Eocytes: A new ribosome structure indicates a kingdom with a close relationship to eukaryotes . In: PNAS . 81, No. 12, June 1984, pp. 3786-3790. doi : 10.1073 / pnas.81.12.3786 . PMID 6587394 . PMC 345305 (free full text). Retrieved October 5, 2012.
- S. Kelly, B. Wickstead, K. Gull: Archaeal phylogenomics provides evidence in support of a methanogenic origin of the Archaea and a thaumarchaeal origin for the eukaryotes . In: Proceedings of the Royal Society B . 278, 2011, pp. 1009-1018. doi : 10.1098 / rspb.2010.1427 . PMID 20880885 . PMC 3049024 (free full text). Retrieved October 5, 2012.
- Anthony M. Poole, Nadja Neumann: Reconciling an archaeal origin of eukaryotes with engulfment: a biologically plausible update of the Eocyte hypothesis . In: Research in Microbiology . 162, 2011, pp. 71-76. doi : 10.1016 / j.resmic.2010.10.002 . Retrieved October 5, 2012.
- Lionel Guy, Thijs JG Ettema: The archaeal 'TACK' superphylum and the origin of eukaryotes . In: Trends in Microbiology . 19, No. 12, December 2011, pp. 580-587. doi : 10.1016 / j.tim.2011.09.002 . PMID 22018741 . Retrieved October 5, 2012.
- Cymon J. Cox, Peter G. Foster, Robert P. Hirt, Simon R. Harris, T. Martin Embley: The archaebacterial origin of eukaryotes . In: PNAS . 105, December 23, 2008, pp. 20356-20361. doi : 10.1073 / pnas.0810647105 . PMID 19073919 . PMC 2629343 (free full text). Retrieved October 5, 2012.
- Anja Spang, Jimmy H. Saw, Steffen L. Jørgensen, Katarzyna Zaremba-Niedzwiedzka, Joran Martijn, Anders E. Lind, Roel van Eijk, Christa Schleper, Lionel Guy, Thijs JG Ettema: Complex archaea that bridge the gap between prokaryotes and eukaryotes . In: Nature . 521, 2015, doi : 10.1038 / nature14447 . PMID 25945739 . PMC 4444528 (free full text). , pp. 173-179.
- Laura Eme, Anja Spang, Jonathan Lombard, Courtney W. Stairs, Thijs JG Ettema: Archaea and the origin of eukaryotes . In: Nature Reviews Microbiology . 15, No. 12, November 10, 2017, , pp. 711-723. doi : 10.1038 / nrmicro.2017.133 .
- Katarzyna Zaremba-Niedzwiedzka et al .: Asgard archaea illuminate the origin of eukaryotic cellular complexity , in: Nature 541, pp. 353–358 of January 19, 2017, doi: 10.1038 / nature21031 .
- NCBI taxonomy page on Archaea .
- Cavalier-Smith T: The phagotrophic origin of eukaryotes and phylogenetic classification of Protozoa . In: Int. J. Syst. Evol. Microbiol. . 52, No. Pt 2, March 2002, pp. 297-354. doi : 10.1099 / 00207713-52-2-297 . PMID 11931142 .
- Regina Saum et al .: The F 1 F O ATP synthase genes in Methanosarcina acetivorans are dispensable for growth and ATP synthesis, in: FEMS Microbiology Letters Vol. 300 Issue 2 of November 2009, pp. 230-236, doi: 10.1111 / j.1574-6968.2009.01785.x
- Elena Hilario, Johann Peter Gogarten: Horizontal transfer of ATPase genes - the tree of life becomes a net of life . In: BioSystems . 31, No. 2-3, 1993, pp. 111-119. doi : 10.1016 / 0303-2647 (93) 90038-E . PMID 8155843 ScienceDirect This article on University of Connecticut (PDF) .
- Armen Y. Mulkidjanian, Michael Y. Galperin, Kira S. Makarova, Yuri I. Wolf, Eugene V. Koonin: Evolutionary primacy of sodium bioenergetics . In: Biology Direct . 3, No. 13, 2008. doi : 10.1186 / 1745-6150-3-13 .
- arms Y. Mulkidjanian, Kira S. Makarova, Michael Y. Galperin, Eugene V. Koonin: Inventing the dynamo machine: the evolution of the F-type and V-type ATPases . In: Nature Reviews Microbiology . 5, No. 11, 2007, pp. 892-899. doi : 10.1038 / nrmicro1767 . This article at Uni Osnabrück: Perspectives (PDF) ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.