| Heterolobosea | |
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| The three different stages of N. fowleri | |
Scientific classification  | |
| Domain: | Eukaryota |
| Phylum: | Percolozoa |
| Class: | Heterolobosea Page & Blanton 1985 |
| Orders | |
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Heterolobosea are a class of Percolozoa. The only member of this group that is infectious to humans is Naegleria fowleri , the causative agent of the often fatal disease amoebic meningitis. Typically, their life cycle alternates between flagellate and amoeboid stages.
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| | This section is empty. You can help by adding to it. (November 2024) |
The first broadly sampled comprehensive phylogenomic (phylotranscriptomic) analysis of the group (from 2025) confirmed the monophyly of Heterolobosea and provided a robustly supported backbone of the phylogeny resulting in the revision of the classification of Heterolobosea to the family level. [1]
The basal split of the cladogram has been confirmed between the subphyla Pharyngomonada (monotypic, with a sole family Pharyngomonadidae) and Tetramitia. In Tetramitia, two main clades (new classes) were identified: Selenaionea, consisting of two orders Neovahlkampfiida and Selenaionida in previously unsuspected but fully supported sister relationship, and Eutetramitea, consisting of orders Creneida, Lyromonadida, Naegleriida (new, including acrasid slime molds), Percolomonadida and Pseudociliatida (represented by the single genus Stephanopogon ; not included in the new analysis but analyses based on 18S rRNA gene sequences have repeatedly shown its close relationship to Percolomonadida with high statistical support): [1]
| Heterolobosea |
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These are collectively referred to as schizopyrenids, amoeboflagellates, or vahlkampfids. They also include the acrasids, a group of social amoebae that aggregate to form sporangia. The entire group is usually called the Heterolobosea, but this may be restricted to members with amoeboid stages.
One Heterolobosea classification system is: [2]
Pleurostomum flabellatum has recently been added to Heterolobosea. [3]
A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word flagellate also describes a particular construction characteristic of many prokaryotes and eukaryotes and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagella. However, several derivations of the term "flagellate" are more formally characterized.
The Percolozoa are a group of colourless, non-photosynthetic Excavata, including many that can transform between amoeboid, flagellate, and cyst stages.
Excavata is an extensive and diverse but paraphyletic group of unicellular 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 Protista kingdom. They were distinguished from other lineages based on electron-microscopic information about how the cells are arranged. They are considered to be a basal flagellate lineage.
Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead united by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major eukaryotic group to be recognized mainly through molecular phylogenies. They are the natural predators of many species of bacteria. They are closely related to the phylum Retaria, comprising amoeboids that usually have complex shells, and together form a supergroup called Rhizaria.
Amoebozoa is a major taxonomic group containing about 2,400 described species of amoeboid protists, often possessing blunt, fingerlike, lobose pseudopods and tubular mitochondrial cristae. In traditional classification schemes, Amoebozoa is usually ranked as a phylum within either the kingdom Protista or the kingdom Protozoa. In the classification favored by the International Society of Protistologists, it is retained as an unranked "supergroup" within Eukaryota. Molecular genetic analysis supports Amoebozoa as a monophyletic clade. Modern studies of eukaryotic phylogenetic trees identify it as the sister group to Opisthokonta, another major clade which contains both fungi and animals as well as several other clades comprising some 300 species of unicellular eukaryotes. Amoebozoa and Opisthokonta are sometimes grouped together in a high-level taxon, named Amorphea. Amoebozoa includes many of the best-known amoeboid organisms, such as Chaos, Entamoeba, Pelomyxa and the genus Amoeba itself. Species of Amoebozoa may be either shelled (testate) or naked, and cells may possess flagella. Free-living species are common in both salt and freshwater as well as soil, moss and leaf litter. Some live as parasites or symbionts of other organisms, and some are known to cause disease in humans and other organisms.
Ancyromonas is a genus of basal Eukaryote consisting of heterotrophic flagellates.
The Tubulinea are a major grouping of Amoebozoa, including most of the more familiar amoebae genera like Amoeba, Arcella, Difflugia and Hartmannella.
Discosea is a class of Amoebozoa, consisting of naked amoebae with a flattened, discoid body shape. Members of the group do not produce tubular or subcylindrical pseudopodia, like amoebae of the class Tubulinea. When a discosean is in motion, a transparent layer called hyaloplasm forms at the leading edge of the cell. In some discoseans, short "subpseudopodia" may be extended from this hyaloplasm, but the granular contents of the cell do not flow into these, as in true pseudopodia. Discosean amoebae lack hard shells, but some, like Cochliopodium and Korotnevella secrete intricate organic scales which may cover the upper (dorsal) surface of the cell. No species have flagella or flagellated stages of life.
Monadofilosa is a grouping of Cercozoa. These organisms are single-celled amoeboid protists.
The family Acrasidae is a family of slime molds which belongs to the excavate group Percolozoa. The name element acrasio- comes from the Greek akrasia, meaning "acting against one's judgement". This group consists of cellular slime molds.
Cafeteria is a genus of marine bicosoecid described in 1988 by Tom Fenchel and D. J. Patterson. It was created after the discovery of a new species, Cafeteria roenbergensis, a tiny (5–10 μm) eukaryotic organism that is eaten by protozoa and small invertebrates. The name is meant to indicate the importance of the genus in the food web.
Schizopyrenida is an order of Heterolobosea.
Jakobids are an order of free-living, heterotrophic, flagellar eukaryotes in the supergroup Excavata. They are small, and can be found in aerobic and anaerobic environments. The order Jakobida, believed to be monophyletic, consists of only twenty species at present, and was classified as a group in 1993. There is ongoing research into the mitochondrial genomes of Jakobids, which are unusually large and bacteria-like, evidence that Jakobids may be important to the evolutionary history of eukaryotes.
Psalteriomonas is a genus of excavates in the group of Heterolobosea. The genus was first discovered and named in 1990. It contains amoeboflagellate cells that live in freshwater anaerobic sediments all over the world. The microtubule-organizing ribbon and the associated microfibrillar bundles of the mastigote system is the predominant feature in Psalteriomonas. This harp-shaped complex gives rise to the name of this genus. Psalteriomonasforms an endosymbiotic relationship with methanogenic bacteria, especially with Methanobacterium formicicum There are currently three species in this genus: P. lanterna, P. vulgaris, and P. magna.
Willaertia /ˈwɪləɹʃə/ is a genus of non-pathogenic, free-living, thermophilic amoebae in the family Vahlkampfiidae.
Thaumatomonas is a genus within Imbricatea of the phylum Cercozoa.
A protist is any eukaryotic organism that is not an animal, plant, or fungus. The protists do not form a natural group, or clade, since they exclude certain eukaryotes with whom they share a common ancestor; but, like algae or invertebrates, the grouping is used for convenience. In some systems of biological classification, such as the popular five-kingdom scheme proposed by Robert Whittaker in 1969, the protists make up a kingdom called Protista, composed of "organisms which are unicellular or unicellular-colonial and which form no tissues". In the 21st century, the classification shifted toward a two-kingdom system of protists: Chromista and Protozoa.
An amoeba, often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopods. Amoebae do not form a single taxonomic group; instead, they are found in every major lineage of eukaryotic organisms. Amoeboid cells occur not only among the protozoa, but also in fungi, algae, and animals.
Endohelea is a proposed clade of eukaryotes that are related to Archaeplastida and the SAR supergroup. They used to be considered heliozoans, but phylogenetically they belong to a group of microorganisms known as Cryptista.
Acrasis kona is a eukaryotic microorganism within the family Acrasidae, notable for its life cycle that alternates between unicellular and multicellular stages.
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