Palpitomonas | |
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Scientific classification | |
Clade: | Cryptista |
Subphylum: | Palpitia |
Class: | Palpitea |
Order: | Palpitida |
Family: | Palpitomonadidae Cavalier-Smith, 2012 |
Genus: | Palpitomonas Yabukii & Ishida, 2010 |
Palpitomonas is a genus of biflagellated protists within the phylum Cryptista , a clade of basal eukaryotes. This genus is especially significant for understanding the early evolution of mitochondria, flagella, and the broader cryptist lineage. Palpitomonas is a key model organism for studying the phylogenetic origins of mitochondria and eukaryotic motility structures, such as flagella. One of the most common species in the genus of Palpitomonas is Palpitomonas bilix , which has been used in genomic and phylogenetic studies due to its special mitochondrial genome structure and basal phylogenetic position. [1] [2] [3]
Palpitomonas is an important organism for research on the origins of eukaryotic life. Palpitomonasbilix have some unique characteristics that are rare in the other eukaryotes, characterized by its small size, biflagellate structure, and unique mitochondrial. The genus Palpitomonas belongs to Cryptista, which includes other simple eukaryotic organisms like cryptophytes and katablepharids. As a bacterivore Palpitomonas plays an ecological role in regulating microbial populations and nutrient cycling in marine ecosystems by feeding on bacteria and become a prey for larger microorganism [1] [2] [3]
The genus Palpitomonas is part of the Cryptista phylum, which itself is situated within the Diaphoretickes supergroup. Cryptista is a basal group of eukaryotes whose members are primarily aquatic and flagellated. The phylum Cryptista, as part of Diaphoretickes, shares a common ancestor with other early-diverging eukaryotic groups, including the Archaeplastida and the SAR supergroup (Stramenopiles, Alveolates, Rhizaria). Classification of Palpitomonas has evolved over time as molecular phylogenetic has revealed its position as one of the earliest-diverging eukaryotic lineages, particularly among the flagellated protists. [1]
The genus Palpitomonas is closely related to other genus of Cryptista, including the Kathablepharids and Cryptophytes, but its specific evolutionary path remains an area of ongoing study. Molecular phylogenetic analyses, particularly those involving ribosomal RNA (rRNA) sequences and protein-coding genes, have demonstrated that Palpitomonas is a basal lineage within Cryptista, with close related to the early-diverging mitochondrial ancestors of other eukaryotes. [1] [2] [3]
Phylogenetic analyses based on multigene datasets have shown Palpitomonasbilix as basal within the Cryptista clade, diverging before cryptophytes and katablepharids. Its unique position in the eukaryotic tree makes it instrumental for studying the divergence of eukaryotic lineages. Palpitomonas is also part of broader studies that question the monophyly of Hacrobia, suggesting complex evolutionary relationships among early-diverging protists. Phylogenetic studies with 157-gene alignments have reinforced its position as a basal cryptist, adding clarity to its relationship with other protists such as cryptophytes. [1] [3]
Palpitomonasbilix, the primary species in this genus, has a distinctive morphology. Cells are small approximately 3-8micrometer with unique structure with two lateral flagella that different in function and position. The anterior flagellum is highly active but the posterior flagellum trails passively, helping the organism's characteristic "wobbling" motion. This biflagellate structure is significant for movement and feeding. Each cell is vacuolated with no cell wall allowing for flexibility. The mitochondria of Palpitomonas contain flat cristae, similar to those found in other cryptists, although distinct from the tubular cristae of Katablepharida. [1] [4]
Ultrastructural analysis shows a single mitochondrion with lobed extensions and an endoplasmic reticulum surrounding the nucleus. A Golgi apparatus is located between the nucleus and flagella, and two microtubular roots support the basal bodies. The anterior flagellum of Palpitomonas possesses mastigonemes—bipartite hair-like structures that aid in movement and feeding by creating a current that draws in food particles. Electron microscopy has showed that Palpitomonas doesn't has ejectosomes an organelle used for rapid ejection of cell contents, which is present in cryptophytes but absent in katablepharids and Palpitomonas. This lack of ejectosomes and other features further distinguishes Palpitomonas from other cryptists. [1] [4]
Palpitomonasbilix has a distinctive mitochondrial genome, organized as a linear DNA molecule with large inverted repeats at both ends. This linear mitochondrial genome structure, unusual among eukaryotes, is thought to have evolved independently in several lineages. It contains genes related to cytochrome c maturation (System I), a system inherited from bacterial ancestors. While related cryptists such as cryptophytes and kathablepharids utilize a different cytochrome c maturation system (System III), Palpitomonas retains the ancestral System I, making it an important model for studying mitochondrial evolution in eukaryotes. [2] [1]
Palpitomonas play an ecological role in marine environment, as a bacterivore by consuming bacteria provide the regulation of bacterial populations and helping in nutrient cycling within microbial communities. As well as its role as prey for larger microorganisms, ecologically Palpitomonas importance in maintaining ecosystem balance in marine environment. [1]
The combination of basal features in Palpitomonas, such as its linear mitochondrial genome and ancestral cytochrome c maturation system, make it an important organism for understanding evolutionary in eukaryotes. Position within Cryptista and Hacrobia and its early diverging lineage provide insights into the development of mitochondria, cellular structures, and other eukaryotic traits. [4] [1] [2]
Palpitomonasbilix was first described in 2010 by Yabuki et al. after being isolated from marine environments near Palau. Observations of its ultrastructure and phylogenetic analyses based on multiple genes led to its classification as a novel genus within Cryptista. This discovery provided new insights into early eukaryotic diversity and clarified the evolutionary links between Cryptista and other early-diverging groups. Palpitomonas remains valuable for studying the diversity of early eukaryotic cells. [2] [4]
Palpitomonas has several vacuoles and an extensive endoplasmic reticulum that surrounding nucleus. Its mitochondria have lobed shape, and the Golgi apparatus located near the flagella processes proteins. The flagellum that moves actively is covered with small hair-like structures called mastigonemes. Unlike other cryptists, P. bilix does not possess ejectosomes, the ejective organelles characteristic of cryptophytes and some kathablepharids. [4] [2]
Palpitomonas reproduces asexually (binary fission) by dividing into two cell. This simple method of reproduction allows Palpitomonas populations to grow quickly in favorable conditions. Unlike other eukaryotes, Palpitomonas does not reproduce sexually, which limits its genetic diversity. However, this basic life cycle reflects its ancient place in eukaryotic history and shares similarities with other early-diverging eukaryotes. [2]
The cryptomonads are a group of algae, most of which have plastids. They are traditionally considered a division of algae among phycologists, under the name of Cryptophyta. They are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, with an anterior groove or pocket. At the edge of the pocket there are typically two slightly unequal flagella. Some may exhibit mixotrophy. They are classified as clade Cryptomonada, which is divided into two classes: heterotrophic Goniomonadea and phototrophic Cryptophyceae. The two groups are united under three shared morphological characteristics: presence of a periplast, ejectisomes with secondary scroll, and mitochondrial cristae with flat tubules. Genetic studies as early as 1994 also supported the hypothesis that Goniomonas was sister to Cryptophyceae. A study in 2018 found strong evidence that the common ancestor of Cryptomonada was an autotrophic protist.
A bikont is any of the eukaryotic organisms classified in the group Bikonta. Many single-celled and multi-celled organisms are members of the group, and these, as well as the presumed ancestor, have two flagella.
Chromalveolata was a eukaryote supergroup present in a major classification of 2005, then regarded as one of the six major groups within the eukaryotes. It was a refinement of the kingdom Chromista, first proposed by Thomas Cavalier-Smith in 1981. Chromalveolata was proposed to represent the organisms descended from a single secondary endosymbiosis involving a red alga and a bikont. The plastids in these organisms are those that contain chlorophyll c.
Telonemia is a phylum of microscopic eukaryotes commonly known as telonemids. They are unicellular free-living flagellates with a unique combination of cell structures, including a highly complex cytoskeleton unseen in other eukaryotes.
Malawimonadidae is a family of unicellular eukaryotes of outsize importance in understanding eukaryote phylogeny.
Malawimonas is genus of unicellular, heterotrophic flagellates with uncertain phylogenetic affinities. They have variably being assigned to Excavata and Loukozoa. Recent studies suggest they may be closely related to the Podiata.
Conosa is a grouping of Amoebozoa. It is subdivided into three groups: Archamoeba, Variosea and Mycetozoa.
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.
The kathablepharids or katablepharids are a group of heterotrophic flagellates closely related to cryptomonads. First described by Heinrich Leonhards Skuja in 1939, kathablepharids were named after the genus Kathablepharis. This genus is corrected to Katablepharis under botanical nomenclature, but the original spelling is maintained under zoological nomenclature. They are single-celled protists with two anteriorly directed flagella, an anterior cytostome for ingesting eukaryotic prey, and a sheath that covers the cell membrane. They have extrusomes known as ejectisomes, as well as tubular mitochondrial cristae.
Telonema is a genus of single-celled organisms.
Collodictyon is a genus of single-celled, omnivorous eukaryotes belonging to the collodictyonids, also known as diphylleids. Due to their mix of cellular components, Collodictyonids do not belong to any well-known kingdom-level grouping of that domain and this makes them distinctive from other families. Recent research places them in a new 'supergroup' together with rigifilids and Mantamonas, with the so-far informal name 'CRuMs'.
Rigifila is a genus of free-living single-celled eukaryotes, or protists, containing the sole species Rigifila ramosa. It is classified within the monotypic family Rigifilidae. Along with Micronucleariidae, it is a member of Rigifilida, an order of basal eukaryotes within the CRuMs clade. It differs from Micronuclearia by having two proteic layers surrounding their cytoplasm instead of a single one, and having more irregular mitochondrial cristae, among other morphological differences.
Diplonemidae is a family of biflagellated unicellular protists that may be among the more diverse and common groups of planktonic organisms in the ocean. Although this family is currently made up of three named genera; Diplonema, Rhynchopus, and Hemistasia, there likely exist thousands of still unnamed genera. Organisms are generally colourless and oblong in shape, with two flagella emerging from a subapical pocket. They possess a large mitochondrial genome composed of fragmented linear DNA. These non-coding sequences must be massively trans-spliced, making it one of the most complicated post-transcriptional editing process known to eukaryotes.
Cryptista is a clade of alga-like eukaryotes. It is most likely related to Archaeplastida which includes plants and many algae, within the larger group Diaphoretickes.
Haptista is a proposed group of protists made up of centrohelids and haptophytes. Phylogenomic studies indicate that Haptista, together with Ancoracysta twista, forms a sister clade to the SAR+Telonemia supergroup, but it may also be sister to the Cryptista (+Archaeplastida). It is thus one of the earliest diverging Diaphoretickes.
Platysulcus tardus is an eukaryotic microorganism that was recently discovered to be the earliest diverging lineage of the Heterokont phylogenetic tree. It is the only member of the family Platysulcidae, order Platysulcida and class Platysulcea.
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.
Palpitea is a proposed clade of eukaryotes that are related to Archaeplastida and the SAR supergroup.
Corbihelia is a proposed phylum of eukaryotes.
Colponema is a genus of single-celled flagellates that feed on eukaryotes in aquatic environments and soil. The genus contains 6 known species and has not been thoroughly studied. Colponema has two flagella which originate just below the anterior end of the cell. One extends forwards and the other runs through a deep groove in the surface and extends backwards. Colponema is a predator that feeds on smaller flagellates using its ventral groove. Like many other alveolates, they possess trichocysts, tubular mitochondrial cristae, and alveoli. It has been recently proposed that Colponema may be the sister group to all other alveolates. The genus could help us understand the origin of alveolates and shed light on features that are ancestral to all eukaryotes.