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Metakaryote
The superkingdom Metakaryota was defined by Thomas Cavalier-Smith as advanced eukaryotes resulting from the endosymbiosis of a proteobacterium, giving rise to the mitochondrion A mitochondrion () is an organelle found in the cell (biology), cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosine tri ..., by an archezoan eukaryote. However, with the collapse of the Archezoa hypothesis (that amitochondriate eukaryotes were basal), this grouping was abandoned in later schemes. In 2023, using molecular phylogenetic analysis of 186 taxa, Al Jewari and Baldauf proposed a phylogenetic tree with the metamonad Parabasalia as basal Eukaryotes. Discoba and the rest of the Eukaryota appear to have emerged as sister taxon to the Preaxostyla, incorporating a single alphaproteobacterium as mitochondria by endosymbiosis. Thus the Fornicata are more closely related to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Martin Embley
Thomas Martin Embley is a British scientist who is a professor at Newcastle University who has made contributions to the understanding of the origin of eukaryotes and the evolution of organelles such as mitochondria, One or more of the preceding sentences incorporates text from the royalsociety.org website where: mitosomes and hydrogenosomes, that are found in parasitic protists. In May 2021, Embley was appointed as a Fellow of the Royal Society. Education Embley was educated at Newcastle University, where he was awarded a PhD on the biology of the bacterium ''Renibacterium salmoninarum ''Renibacterium salmoninarum'' is a member of the Micrococcaceae family. It is a Gram-positive, intracellular bacterium that causes disease in young salmonid fish. The infection is most commonly known as "bacterial kidney disease" but may also b ...'' in 1983. References {{DEFAULTSORT:Embley, Martin Fellows of the Royal Society Fellows of the Academy of Medical Sciences (United Kingdo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parabasalid
The parabasalids are a group of flagellated protists within the supergroup Excavata. Most of these eukaryotic organisms form a symbiosis, symbiotic relationship in animals. These include a variety of forms found in the intestines of termites and cockroaches, many of which have symbiotic bacteria that help them digest cellulose in woody plants. Other species within this supergroup are known parasites, and include human pathogens. Characteristics The flagella are arranged in one or more clusters near the anterior of the cell. Their basal bodies are linked to parabasal fibers that are associated with a prominent Golgi apparatus, Golgi complex, together forming a parabasal apparatus distinctive to the group. Attachment of a parabasal fiber to the first Golgi cisterna by thin filaments has been reported in ''Tritrichomonas foetus''. Usually they also give rise to a sheet of cross-like microtubules that runs down the center of the cell and in some cases projects past the end. This i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyanobacterium
Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteria's informal common name, blue-green algae. Cyanobacteria are probably the most numerous taxon to have ever existed on Earth and the first organisms known to have produced oxygen, having appeared in the middle Archean eon and apparently originated in a freshwater or terrestrial environment. Their photopigments can absorb the red- and blue-spectrum frequencies of sunlight (thus reflecting a greenish color) to split water molecules into hydrogen ions and oxygen. The hydrogen ions are used to react with carbon dioxide to produce complex organic compounds such as carbohydrates (a process known as carbon fixation), and the oxygen is released as a byproduct. By continuously producing and releasing oxygen over billions of years, cyanobacteria ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SAR Supergroup
SAR is a highly diverse clade of eukaryotes, often considered a supergroup, that includes stramenopiles (heterokonts), alveolates, and rhizarians. It is a node-based taxon (under the Sar name), including all descendants of the three groups' last common ancestor, and comprises most of the now-rejected Chromalveolata. Their sister group has been found to be telonemids, with which they make up the TSAR clade. Harosa is sometimes used synonymously with TSAR. Etymology The name SAR is an acronym derived from the first letters of its three constituent clades; it has been alternatively spelled RAS. The term Harosa (at the subkingdom level) has also been used, with Stramenopiles replaced by its synonym Heterokonta in this variant of the acronym. History of discovery Before the discovery of the SAR supergroup, stramenopiles and alveolates were classified in the supergroup Chromalveolata alongside haptophytes and cryptomonads, being believed to have acquired plastids th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amorphea
Amorphea is a taxonomic supergroup that includes the basal Amoebozoa and Obazoa. That latter contains the Opisthokonta, which includes the fungi, animals and the choanoflagellates. The taxonomic affinities of the members of this clade were originally described and proposed by Thomas Cavalier-Smith in 2002. The International Society of Protistologists, the recognised body for taxonomy of protozoa, recommended in 2012 that the term Unikont be changed to Amorphea because the name "Unikont" is based on a hypothesized synapomorphy that the ISOP authors and other scientists later rejected. It includes amoebozoa, opisthokonts, and apusomonads. Taxonomic revisions within this group Thomas Cavalier-Smith proposed two new phyla: Sulcozoa, which consists of the subphyla Apusozoa ( Apusomonadida and Breviatea), and Varisulca, which includes the subphyla Diphyllatea, Discocelida, Mantamonadidae, Planomonadida and Rigifilida. Further work by Cavalier-Smith showed that Sul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neokaryotes
The neokaryotes (Cavalier-Smith 1993) are a proposed eukaryote clade consisting of the unikonts and the bikonts as sister of for instance the Jakobea. It arises because the Euglenozoa, Percolozoa, Tsukubea, and Jakobea are seen in this view as more basal eukaryotes. These four groups, are traditionally grouped together in the Discoba. However, the Discoba may well be paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ... as the neokaryotes may have emerged in them. The group was recovered as a monophyletic group in a later analysis, Al Jewari and Baldauf (2023). Taxonomy A proposed cladogram is References Eukaryote taxa {{Eukaryote-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euglenozoa
Euglenozoa are a large group of flagellate Discoba. They include a variety of common free-living species, as well as a few important parasites, some of which infect humans. Euglenozoa are represented by four major groups, ''i.e.,'' Kinetoplastea, Diplonemea, Euglenida, and Symbiontida. Euglenozoa are unicellular, mostly around in size, although some euglenids get up to long. Structure Most euglenozoa have two flagella, which are inserted parallel to one another in an apical or subapical pocket. In some these are associated with a cytostome or mouth, used to ingest bacteria or other small organisms. This is supported by one of three sets of microtubules that arise from the flagellar bases; the other two support the dorsal and ventral surfaces of the cell. Some other euglenozoa feed through absorption, and many euglenids possess chloroplasts, the only eukaryotes outside Diaphoretickes to do so without performing kleptoplasty, and so obtain energy through photosynthesis. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Percolozoa
The Percolozoa are a group of colourless, non-photosynthetic excavates, including many that can transform between amoeboid, flagellate, and cyst stages. Characteristics Most Percolozoa are found as bacterivores in soil, fresh water and occasionally in the ocean. The only member of this group that is infectious to humans is '' Naegleria fowleri'', the causative agent of the often fatal disease amoebic meningitis. The group is closely related to the Euglenozoa, and share with them the unusual characteristic of having mitochondria with discoid cristae. The presence of a ventral feeding groove in the flagellate stage, as well as other features, suggests that they are part of the Excavata group. The amoeboid stage is roughly cylindrical, typically around 20–40 μm in length. They are traditionally considered lobose amoebae, but are not related to the others, and unlike them, do not form true lobose pseudopods. Instead, they advance by eruptive waves, where hemispherical bulges ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jakoba
''Jakoba'' is a genus in the taxon Excavata, and currently has a single described species, ''Jakoba libera'' described by David_J._Patterson, Patterson in 1990, and named in honour of Dutch botanist (Algology, Myology and Lichenology) Jakoba Ruinen. (Previously described ''Jakoba incarcerata'' has been renamed ''Andalucia incarcerata'', and ''Jakoba bahamensis'' /''Jakoba bahamiensis'' is not formally described.) Appearance and characteristics ''Jakoba'' are small bacterivorous zooflagellates (jakobids) found in marine and hypersaline environments. They are free swimming trophic cells with two Flagellum, flagella and range between five and ten micrometers in length. Cells rotate along their longitudinal axis to allow for swimming in straight lines unless deformation and “squirming” occurs due to compression in debris. During feeding, bacteria are removed from the water column by a current created by the posterior flagellum. This current causes the bacteria to collect in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Discoba
Excavata is an obsolete, extensive and diverse Paraphyly, paraphyletic group of unicellular Eukaryote, Eukaryota. The group was first suggested by Simpson and Patterson in 1999 and the name latinized and assigned a rank by Thomas Cavalier-Smith in 2002. It contains a variety of free-living and symbiotic protists, and includes some important parasites of humans such as ''Giardia'' and ''Trichomonas''. Excavates were formerly considered to be included in the now- obsolete Protist, Protista kingdom. They were distinguished from other lineages based on electron-microscopic information about how the cells are arranged (they have a distinctive ultrastructural identity). They are considered to be a Basal_(phylogenetics), basal flagellate lineage. On the basis of phylogenomic analyses, the group was shown to contain three widely separated eukaryote groups, the discobids, metamonads, and malawimonads. A current view of the composition of the excavates is given below, indicating that th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alphaproteobacteria
''Alphaproteobacteria'' or ''α-proteobacteria'', also called ''α-Purple bacteria'' in earlier literature, is a class of bacteria in the phylum '' Pseudomonadota'' (formerly "Proteobacteria"). The '' Magnetococcales'' and '' Mariprofundales'' are considered basal or sister to the ''Alphaproteobacteria''. The ''Alphaproteobacteria'' are highly diverse and possess few commonalities, but nevertheless share a common ancestor. Like all ''Proteobacteria'', its members are gram-negative, although some of its intracellular parasitic members lack peptidoglycan and are consequently gram variable. Characteristics The ''Alphaproteobacteria'' are a diverse taxon and comprise several phototrophic genera, several genera metabolising C1-compounds (e.g. ''Methylobacterium'' spp.), symbionts of plants (e.g. '' Rhizobium'' spp.), endosymbionts of arthropods ('' Wolbachia'') and intracellular pathogens (e.g. '' Rickettsia''). Moreover, the class is sister to the protomitochondrion, the bacterium ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Preaxostyla
Anaeromonadea, also known as Preaxostyla, is a class of excavate protists, comprising the oxymonads, '' Trimastix'', and '' Paratrimastix''. This group is studied as a model system for reductive evolution of mitochondria, because it includes both organisms with anaerobic mitochondrion-like organelles ('' Trimastix'' and '' Paratrimastix''), and those that have completely lost their mitochondria ( oxymonads ''Monocercomonoides'', ''Streblomastix A symbiotic eukaryote that lives in the hindgut of termites, ''Streblomastix'' is a protist associated with a community of ectosymbiotic bacteria. Motility ''Streblomastix'' moves by beating its anterior flagella. Morphology These protists ...'', and '' Blattamonas''). Phylogeny and Taxonomy Based on the work of Zhang et al. 2015. References External links Tree of Life: Preaxostyla Metamonads {{Excavata-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
