Mastigamoeba

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Mastigamoeba
Algen I. (Schizophyceen, Flagellaten, Peridineen) (1910) (17950796051).jpg
Mastigamoeba spp., fig. 3-4, fig. 16-18
Scientific classification
Domain:
(unranked):
Class:
Family:
Genus:
Mastigamoeba
Species

M. aspera
M. balamuthi
M. hylae
M. longfilum
M. punctachora
M. schizophrenia
M. setosa
M. simplex

Contents

Synonyms

Phreatamoeba
Mastigina

Mastigamoeba is a genus of pelobionts, and treated by some as members of the Archamoebae group of protists. Mastigamoeba are characterized as anaerobic, amitochondriate organisms that are polymorphic. Their dominant life cycle stage is as an amoeboid flagellate. Species are typically free living, though endobiotic species have been described.

The genus is relatively understudied, and under contention regarding the composition of the genus. While dozens of species have been described (some in other genera such as Phreatamoeba, Dinamoeba, and Mastigina), the well described species are Mastigamoeba aspera Schulze, 1875; Mastigamoeba simplex Kent, 1880; Mastigamoeba chlamys Frenzel, 1897 Lemmermann, 1914; Mastigamoeba viridis Prowazek, 1900; Mastigamoeba trichophora Lauterborn, 1901; Mastigamoeba balamuthi (Chàvez et al., 1986) Simpson et al., 1997; Mastigamoeba schizophrenia Simpson et al., 1997; and Mastigamoeba punctachora Bernard, Simpson and Patterson, 2000. Mastigamoeba balamuthi was initially referred to as Phreatamobea balamuthi and are treated by some as indistinguishable at the generic level, though this is not universally accepted. [1] All species share many similarities with other pelobionts, such as Mastigella and the related Entamoeba.


It includes Mastigamoeba balamuthi . [2]

A strain previously called as Mastigamoeba invertens (ATCC 50338) is now classified as Breviata anathema. [3]

History

Mastigamoeba was described as a genus of species characterized by an ameboid body with a hyaline based cytoplasm and a flagellum. Due to its similarities to genera such as Mastigella and Mastigina, the genus Mastigamoeba was specified in 1891 to only include organisms with the following features: amoeboid flagellates with hyaline based cytoplasm, a direct connection between the flagellum and the nucleus, on occasions with lateral pseudopods, and nucleus with an elongated shape. [4] Throughout the 20th century, hundreds of species were described under the genus Mastigamoeba based on external morphological characteristics alone. However, recent discoveries regarding life cycles have shown that a single organism takes on many morphologies throughout its life cycle, putting the number of described species into question. [5] There are currently 9 confirmed distinguished species of Mastigamoeba, with many more in contention. Tom Cavalier-Smith described the class Archamoebae in 1983 and among others included the order Mastigamoebid, which includes the genus Mastigamoeba [6]

Historically, amoeboid flagellates have been considered Pelobionts, which encompasses mastigamoebids and pelomyxids. [6]


Habitat and Ecology

Mastigamoebae are a type of Pelobiont. Pelobionts are considered microoxic; they thrive in environments with 10-20% of atmospheric oxygen such as in upper mud or sand layers, or the water-sediment surface of shallow ponds. Some have been found in sewage treatment plants. Pelobionts are typically found worldwide, with studies confirming their extensive presence in temperate regions of Europe and North America. [7] Habitats typically include freshwater rivers and lakes, with the highest abundance of organisms in stagnant water, where low-oxygen environments are common. Marine environments are also found to host pelobionts. Habitats in which pelobionts are found are organically rich.

Though most pelobionts are free-living, some members are considered endobiotic, meaning they survive only in the guts of hosts. These members are completely anoxic, and thrive in areas of low pH. They have been found in various vertebrate and invertebrate hosts, particularly within primates and dogs. [8]

Description

Mastigamoeba are characterized as amoeboid flagellates with hyaline cytoplasm. The hyaline cytoplasm is clear. Mastigamoeba are polymorphic; they switch between multiple morphologies throughout their life cycles. They can exist as amoeboid flagellates, aflagellate amoebae, multinucleate amoebae, and as cysts. [9]

Mastigamoeba are divided into two main clades. Clade A includes those species that are large with a broader and larger flagellum (e.g., M. balamuthi). Clade B includes those that are smaller, with narrow flagella (e.g., M. simplex). Uroids are present in Type A species, whereas Type B species feature a trailing pseudopod instead. Type A species typically grow to 200 μm in length, and Type B species are typically smaller than 80 μm in length. The flagellum ranges in length from 10 μm to 60 μm. [10]

The singular flagellum is composed of a 9 + 2 microtubule structure. The flagellar apparatus consists of a single basal body, from which the flagellum arises. There is a microtubular cone that directly connects the flagellar apparatus to the nucleus. In Type A species, this cone is wide, and arises from the base and the lateral ends of the basal body. In Type B species, this cone is narrow, and arises only from the base of the basal body. The flagellar apparatus is positioned anteriorly and aids in movement. [4]

The exterior of the cell is covered in a thin, unevenly distributed layer of organic filamentous material. These filaments run parallel to the cell and are 1 μm at their thickest point. The chemical composition of this extracellular covering is unknown. Some Mastigamoeba have spines distributed irregularly around the cell. These spines are hollow, and their composition is unknown. The organic layer sometimes contains symbionts of prokaryotic origin. The identity and relationship of these symbionts is unknown. [11]

The cyst stage is surrounded by a wall of unknown composition. The cyst stage is uninucleate, and filled with granules. [9]

Mastigamoeba lack Golgi dictyosomes, though core Golgi functions are retained by related elements in the endomembrane system. The endoplasmic reticulum contains some bundled structures, and various vesicles that fulfil the core functions of a Golgi dictyosome.

Peroxisomes are not present in all Archamoebae. Studies show that some Mastigamoeba contain peroxisomal proteins.

Archamoebae are all amitochondriate, meaning they lack typical mitochondria. Mitochondria in Mastigamoeba have been reduced to or changed to forms that still retain some mitochondrial function or have altered functions.

Species such as M. balamuthi have mitochondrial related organelles called hydrogenosomes. These function to produce ATP by partial anaerobic oxidation of pyruvate. Hydrogenosomes have lost their genome, and the electron-transport chain. They produce Hydrogen gas as a by-product. Hydrogenosomes have been formed from mitochondria through loss of aerobic life stages. The biosynthesis of iron-sulfur clusters has transitioned to be a cytosolic function through a lateral gene transfer event. [12]

Other species have reduced mitochondrial organelles called mitosomes. These have reduced so far that their only function is the biosynthesis of iron-sulfur clusters. They have no energy metabolic function, and as a result the organisms must attain energy by other means. To make up for the loss of ATP production, amitochondriate organisms have acquired the ability to import ATP. [12]

The main trophic form of Mastigamoeba is a uninucleate amoeboid flagellate, though some species have multinucleate morphologies. M. schizophrenia has up to 10 nuclei in its multinucleate stage. [13] In M. balamuthi, the dominant trophic form is as a multinucleate, in which it can have up to 46 nuclei. Reproduction occurs by mitosis and subsequent budding. When multinucleate, this results in unequal nuclei amongst daughter cells. [9]

Practical Importance

Mastigamoeba balamuthi is the most well-known species of Mastigamoeba, as it has served as a model organism for study and research regarding amitochondriate organisms. [14] The method of iron-sulfur cluster biosynthesis and how it has moved from the mitochondria to the cytosol has been extensively studied in M. balamuthi. The mitochondrial remnants in M. balamuthi are thought to be an intermediate degenerate stage between a typical mitochondria and more reduced mitosomes found in other pelobionts. [2]

Related Research Articles

<span class="mw-page-title-main">Excavata</span> Supergroup of unicellular organisms belonging to the domain Eukaryota

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.

In biology, Archezoa is a term that has been introduced by several authors to refer to a group of organisms. Authors include Josef Anton Maximilian Perty, Ernst Haeckel and in the 20th century by Thomas Cavalier-Smith in his classification system. Each author used the name to refer to different arrays of organisms. This reuse by later authors of the same taxon name for different groups of organisms is widely criticized in taxonomy because the inclusion of the name in a sentence does not make sense unless the particular usage is specified. Nonetheless, all uses of 'Archezoa' are now obsolete.

<span class="mw-page-title-main">Parabasalid</span> Group of flagellated protists

The parabasalids are a group of flagellated protists within the supergroup Excavata. Most of these eukaryotic organisms form a 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.

<i>Pelomyxa</i> Genus of flagellar amoeboids

Pelomyxa is a genus of giant flagellar amoebae, usually 500–800 μm but occasionally up to 5 mm in length, found in anaerobic or microaerobic bottom sediments of stagnant freshwater ponds or slow-moving streams.

<span class="mw-page-title-main">Hydrogenosome</span> Mitochondrion-derived organelle

A hydrogenosome is a membrane-enclosed organelle found in some anaerobic ciliates, flagellates, and fungi. Hydrogenosomes are highly variable organelles that have presumably evolved from protomitochondria to produce molecular hydrogen and ATP in anaerobic conditions.

The Oxymonads are a group of flagellated protists found exclusively in the intestines of animals, mostly termites and other wood-eating insects. Along with the similar parabasalid flagellates, they harbor the symbiotic bacteria that are responsible for breaking down cellulose. There is no evidence for presence of mitochondria in oxymonads and three species have been shown to completely lack any molecular markers of mitochondria.

A mitosome is a mitochondrion-related organelle (MRO) found in a variety of parasitic unicellular eukaryotes, such as members of the supergroup Excavata. The mitosome was first discovered in 1999 in Entamoeba histolytica, an intestinal parasite of humans, and mitosomes have also been identified in several species of Microsporidia and in Giardia intestinalis.

<span class="mw-page-title-main">Archamoebae</span> Phylum of protists

The Archamoebae are a group of protists originally thought to have evolved before the acquisition of mitochondria by eukaryotes. They include genera that are internal parasites or commensals of animals. A few species are human pathogens, causing diseases such as amoebic dysentery. The other genera of archamoebae live in freshwater habitats and are unusual among amoebae in possessing flagella. Most have a single nucleus and flagellum, but the giant amoeba Pelomyxa has many of each.

<i>Breviata</i> Genus of flagellated amoebae

Breviata anathema is a single-celled flagellate amoeboid eukaryote, previously studied under the name Mastigamoeba invertens. The cell lacks mitochondria, much like the pelobionts to which the species was previously assigned, but has remnant mitochondrial genes, and possesses an organelle believed to be a modified anaerobic mitochondrion, similar to the mitosomes and hydrogenosomes found in other eukaryotes that live in low-oxygen environments.

Carpediemonas is genus of Metamonada, and belongs to the group Excavata. This organism is a unicellular flagellated eukaryote that was first discovered in substrate samples from the Great Barrier Reef. Carpediemonas can be found in anaerobic intertidal sediment, where it feeds on bacteria. A feature of this species is the presence of a feeding groove, a characteristic of the excavates. Like most other metamonads, Carpediemonas does not rely on an aerobic mitochondrion to produce energy. Instead, it contains hydrogenosomes that are used to produce ATP. This organism has two flagella: a posterior one used for feeding on the substrate, and an anterior one that moves in a slower sweeping motion. Carpediemonas is assigned to the fornicates, where similar Carpediemonas-like organisms are used in researching the evolution within excavates. Although Carpediemonas is a member of the metamonads, it is unusual in the sense that it is free-living and has three basal bodies.

Trimastix is a genus of excavate protists, the sole occupant of the order Trimastigida. Trimastix are bacterivorous, free living and anaerobic. It was first observed in 1881 by William Kent. There are few known species, and the genus's role in the ecosystem is largely unknown. However, it is known that they generally live in marine environments within the tissues of decaying organisms to maintain an anoxic environment. Much interest in this group is related to its close association with other members of Preaxostyla. These organisms do not have classical mitochondria, and as such, much of the research involving these microbes is aimed at investigating the evolution of mitochondria.

<span class="mw-page-title-main">Conosa</span> Phylum of protozoans

Conosa is a grouping of Amoebozoa. It is subdivided into three groups: Archamoeba, Variosea and Mycetozoa.

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.

<span class="mw-page-title-main">Breviatea</span> Group of protists

Breviatea, commonly known as breviate amoebae, are a group of free-living, amitochondriate protists with uncertain phylogenetic position. They are biflagellate, and can live in anaerobic (oxygen-free) environments. They are currently placed in the Obazoa clade. They likely do not possess vinculin proteins. Their metabolism relies on fermentative production of ATP as an adaptation to their low-oxygen environment.

Monocercomonoides is a genus of flagellate Excavata belonging to the order Oxymonadida. It was established by Bernard V. Travis and was first described as those with "polymastiginid flagellates having three anterior flagella and a trailing one originating at a single basal granule located in front of the anteriorly positioned nucleus, and a more or less well-defined axostyle". It is the first eukaryotic genus to be found to completely lack mitochondria, and all hallmark proteins responsible for mitochondrial function. The genus also lacks any other mitochondria related organelles (MROs) such as hydrogenosomes or mitosomes. Data suggests that the absence of mitochondria is not an ancestral feature, but rather due to secondary loss. Monocercomonoides sp. was found to obtain energy through an enzymatic action of nutrients absorbed from the environment. The genus has replaced the iron-sulfur cluster assembly pathway with a cytosolic sulfur mobilization system, likely acquired by horizontal gene transfer from a eubacterium of a common ancestor of oxymonads. These organisms are significant because they undermine assumptions that eukaryotes must have mitochondria to properly function. The genome of Monocercomonoides exilis has approximately 82 million base pairs, with 18 152 predicted protein-coding genes.

Stygiella /ˌstɪ.d͡ʒiˈɛ.lə/ is a genus of free-living marine flagellates belonging to the family Stygiellidae in the jakobids (excavata).

Anaeramoeba is a genus of anaerobic protists of uncertain phylogenetic position, first described in 2016.

<i>Syssomonas</i> Genus of protists

Syssomonas is a monotypic genus of unicellular flagellated protists containing the species Syssomonas multiformis. It is a member of Pluriformea inside the lineage of Holozoa, a clade containing animals and their closest protistan relatives. It lives in freshwater habitats. It has a complex life cycle that includes unicellular amoeboid and flagellated phases, as well as multicellular aggregates, depending on the growth medium and nutritional state.

<i>Paratrimastix pyriformis</i> Species of protists

Paratrimastix pyriformis is a species of free-living (non-parasitic) anaerobic freshwater bacteriovorous flagellated protists formerly known as Trimastix pyriformis and Tetramitus pyriformis.

<i>Idionectes</i> Species of amoeba

Idionectes is a genus of amoeba discovered from Allensbach, Konstanz, Germany. It contains only one species, I. vortex. Described by Sebastian Hess and Alastair G. B. Simpson in 2019, the scientific name means distinct or peculiar swimmer. Named because of its unique locomotion by creating a water vortex with its flying saucer-like body, it was also dubbed UFO. It is the only known eukaryotic cell having a rotating flagellum, which is the usual characteristic of prokaryotes.

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