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, the term "flagellate" is included in other terms which are more formally characterized.
The Stramenopiles, also called Heterokonts, are a clade of organisms distinguished by the presence of stiff tripartite external hairs. In most species, the hairs are attached to flagella, in some they are attached to other areas of the cellular surface, and in some they have been secondarily lost. Stramenopiles represent one of the three major clades in the SAR supergroup, along with Alveolata and Rhizaria.
A flagellum is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates.
Chlamydomonas is a genus of green algae consisting of about 150 species of unicellular flagellates, found in stagnant water and on damp soil, in freshwater, seawater, and even in snow as "snow algae". Chlamydomonas is used as a model organism for molecular biology, especially studies of flagellar motility and chloroplast dynamics, biogenesis, and genetics. One of the many striking features of Chlamydomonas is that it contains ion channels (channelrhodopsins) that are directly activated by light. Some regulatory systems of Chlamydomonas are more complex than their homologs in Gymnosperms, with evolutionarily related regulatory proteins being larger and containing additional domains.
The synurids are a small group of heterokont algae, found mostly in freshwater environments, characterized by cells covered in silica scales.
Pedinellales is a group of single-celled algae found in both marine environments and freshwater.
The axodines are a group of unicellular stramenopiles that includes silicoflagellate and rhizochromulinid algae, actinomonad heterotrophic flagellates and actinophryid heliozoa. Alternative classifications treat the dictyochophytes as heterokont algae, or as Chrysophyceae. Other overlapping taxonomic concepts include the Actinochrysophyceae, Actinochrysea or Dictyochophyceae sensu lato. The grouping was proposed on the basis of ultrastructural similarities, and is consistent with subsequent molecular comparisons.
Oomycota forms a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms, called oomycetes. They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the result of contact between hyphae of male antheridia and female oogonia; these spores can overwinter and are known as resting spores. Asexual reproduction involves the formation of chlamydospores and sporangia, producing motile zoospores. Oomycetes occupy both saprophytic and pathogenic lifestyles, and include some of the most notorious pathogens of plants, causing devastating diseases such as late blight of potato and sudden oak death. One oomycete, the mycoparasite Pythium oligandrum, is used for biocontrol, attacking plant pathogenic fungi. The oomycetes are also often referred to as water molds, although the water-preferring nature which led to that name is not true of most species, which are terrestrial pathogens.
The Chrysophyceae, usually called chrysophytes, chrysomonads, golden-brown algae or golden algae are a large group of algae, found mostly in freshwater. Golden algae is also commonly used to refer to a single species, Prymnesium parvum, which causes fish kills.
Cafeteria roenbergensis is a small bacterivorous marine flagellate. It was discovered by Danish marine ecologist Tom Fenchel and named by him and taxonomist David J. Patterson in 1988. It is in one of three genera of bicosoecids, and the first discovered of two known Cafeteria species. Bicosoecids belong to a broad group, the stramenopiles, also known as heterokonts (Heterokonta) that includes photosynthetic groups such as diatoms, brown, and golden algae, and non-photosynthetic groups such as opalinids, actinophryid "heliozoans", and oomycetes. The species is found primarily in coastal waters where there are high concentrations of bacteria on which it grazes. Its voracious appetite plays a significant role in regulating bacteria populations.
In botany, a zoid or zoïd is a reproductive cell that possesses one or more flagella, and is capable of independent movement. Zoid can refer to either an asexually reproductive spore or a sexually reproductive gamete. In sexually reproductive gametes, zoids can be either male or female depending on the species. For example, some brown alga (Phaeophyceae) reproduce by producing multi-flagellated male and female gametes that recombine to form the diploid sporangia. Zoids are primarily found in some protists, diatoms, green alga, brown alga, non-vascular plants, and a few vascular plants. The most common classification group that produces zoids is the heterokonts or stramenopiles. These include green alga, brown alga, oomycetes, and some protists. The term is generally not used to describe motile, flagellated sperm found in animals. Zoid is also commonly confused for zooid which is a single organism that is part of a colonial animal.
The raphidophytes, formally known as Raphidomonadea or Raphidophyceae, are a small group of eukaryotic algae that includes both marine and freshwater species. All raphidophytes are unicellular, with large cells, but no cell walls. Raphidophytes possess a pair of flagella, organised such that both originate from the same invagination. One flagellum points forwards, and is covered in hair-like mastigonemes, while the other points backwards across the cell surface, lying within a ventral groove. Raphidophytes contain numerous ellipsoid chloroplasts, which contain chlorophylls a, c1 and c2. They also make use of accessory pigments including β-carotene and diadinoxanthin. Unlike other heterokontophytes, raphidophytes do not possess the photoreceptive organelle typical of this group.
Nephroselmis is a genus of green algae. It has been placed in the family Nephroselmidaceae, although a 2009 study suggests that it should be separated into its own class, Nephroselmidophyceae. One species can be an endosymbiont of Hatena arenicola.
The genus Labyrinthula is part of the protist group Labyrinthulomycetes and contains thirteen species. The major feature of this genus is the formation of an ectoplasmic net secreted by specialized organelles called bothrosomes which surrounds the colony, which is also used by Labyrinthula for moving. The protist reproduces by zoosporulation as it sets some flagellated spores free from a sporangium. One of the flagella of the zoospores has stiff tripartite hairs (mastigonemes) - the defining characteristic of the stramenopiles.
Proteromonas is a genus of single-celled biflagellated microbial eukaryotes belonging to the Superphylum Stramenopiles which are characterized by the presence of tripartite, hair-like structures on the anteriorly-directed larger of the two flagella. Proteromonas on the other hand are notable by having tripartite hairs called somatonemes not on the flagella but on the posterior of the cell. Proteromonas are closely related to Karotomorpha and Blastocystis, which belong to the Opalines group.
A polar organelle is a structure at a specialised region of the bacterial polar membrane that is associated with the flagellar apparatus. This flagellum-associated structure can easily be distinguished from the other membrane regions in ultrathin sections of embedded bacteria by electron microscopy when the cell membrane is orientated perpendicular to the viewing direction. There, the membrane appears slightly thickened with a finely frilled layer facing the inside of the cell. It is also possible to isolate these polar organelles from the bacterial cells and study them in face view in negatively stained preparations.
Platysulcus 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, of uncertain taxonomic position within the phylum Bigyra. It contains the only species P. tardus.
Synura is a genus of colonial chrysomonad algae covered in silica scales. It is the most conspicuous genus of the order Synurales.
Rhodelphis is a single-celled archaeplastid that lives in aquatic environments and is the sister group to red algae and possibly Picozoa. While red algae have no flagellated stages and are generally photoautotrophic, Rhodelphis is a flagellated predator containing a non-photosynthetic plastid. This group is important to the understanding of plastid evolution because they provide insight into the morphology and biochemistry of early archaeplastids. Rhodelphis contains a remnant plastid that is not capable of photosynthesis, but may play a role in biochemical pathways in the cell like heme synthesis and iron-sulfur clustering. The plastid does not have a genome, but genes are targeted to it from the nucleus. Rhodelphis is ovoid with a tapered anterior end bearing two perpendicularly-oriented flagella.
Ultrastructural identity is a concept in biology. It asserts that evolutionary lineages of eukaryotes in general and protists in particular can be distinguished by complements and arrangements of cellular organelles. These ultrastructural components can be visualized by electron microscopy.
