Euglena

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Euglena
Euglena - 400x (8999902391).jpg
Euglena sp.
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Phylum: Euglenozoa
Class: Euglenoidea
Order: Euglenales
Family: Euglenaceae
Genus: Euglena
Ehrenberg, 1830

Euglena is a genus of single cell flagellate eukaryotes. It is the best known and most widely studied member of the class Euglenoidea, a diverse group containing some 54 genera and at least 200 species. [1] [2] Species of Euglena are found in fresh water and salt water. They are often abundant in quiet inland waters where they may bloom in numbers sufficient to color the surface of ponds and ditches green ( E. viridis ) or red ( E. sanguinea ). [3]

Contents

The species Euglena gracilis has been used extensively in the laboratory as a model organism. [4]

Most species of Euglena have photosynthesizing chloroplasts within the body of the cell, which enable them to feed by autotrophy, like plants. However, they can also take nourishment heterotrophically, like animals. Since Euglena have features of both animals and plants, early taxonomists, working within the Linnaean two-kingdom system of biological classification, found them difficult to classify. [5] [6] It was the question of where to put such "unclassifiable" creatures that prompted Ernst Haeckel to add a third living kingdom (a fourth kingdom in toto) to the Animale, Vegetabile (and Lapideum meaning Mineral) of Linnaeus: the Kingdom Protista. [7]

Form and function

When feeding as a heterotroph, Euglena takes in nutrients by osmotrophy, and can survive without light on a diet of organic matter, such as beef extract, peptone, acetate, ethanol or carbohydrates. [8] [9] When there is sufficient sunlight for it to feed by phototrophy, it uses chloroplasts containing the pigments chlorophyll a and chlorophyll b to produce sugars by photosynthesis. [10] Euglena's chloroplasts are surrounded by three membranes, while those of plants and the green algae (among which earlier taxonomists often placed Euglena) have only two membranes. This fact has been taken as morphological evidence that Euglena's chloroplasts evolved from a eukaryotic green alga. [11] Thus, the similarities between Euglena and plants would have arisen not because of kinship but because of a secondary endosymbiosis. Molecular phylogenetic analysis has lent support to this hypothesis, and it is now generally accepted. [12] [13]

Diagram of Euglena (by Patrick Keeling and Yana Eglit) Euglenid body plan.jpg
Diagram of Euglena (by Patrick Keeling and Yana Eglit)

Euglena chloroplasts contain pyrenoids, used in the synthesis of paramylon, a form of starch energy storage enabling Euglena to survive periods of light deprivation. The presence of pyrenoids is used as an identifying feature of the genus, separating it from other euglenoids, such as Lepocinclis and Phacus . [14]

Euglena have two flagella rooted in basal bodies located in a small reservoir at the front of the cell. Typically, one flagellum is very short, and does not protrude from the cell, while the other is long enough to be seen with light microscopy. In some species, such as Euglena mutabilis, both flagella are "non-emergent"—entirely confined to the interior of the cell's reservoir—and consequently cannot be seen in the light microscope. [15] [16] In species that possess a long, emergent flagellum, it may be used to help the organism swim. [17] The surface of the flagellum is coated with about 30,000 extremely fine filaments called mastigonemes. [18]

Like other euglenoids, Euglena possess a red eyespot, an organelle composed of carotenoid pigment granules. The red spot itself is not thought to be photosensitive. Rather, it filters the sunlight that falls on a light-detecting structure at the base of the flagellum (a swelling, known as the paraflagellar body), allowing only certain wavelengths of light to reach it. As the cell rotates with respect to the light source, the eyespot partially blocks the source, permitting the Euglena to find the light and move toward it (a process known as phototaxis). [19]

Spiral pellicle strips Euglena pellicle 2.jpg
Spiral pellicle strips

Euglena lacks a cell wall. Instead, it has a pellicle made up of a protein layer supported by a substructure of microtubules, arranged in strips spiraling around the cell. The action of these pellicle strips sliding over one another, known as metaboly, gives Euglena its exceptional flexibility and contractility. [19] The mechanism of this euglenoid movement is not understood, but its molecular basis may be similar to that of amoeboid movement. [20]

In low moisture conditions, or when food is scarce, Euglena forms a protective wall around itself and lies dormant as a resting cyst until environmental conditions improve.

Reproduction

Euglena reproduce asexually through binary fission, a form of cell division. Reproduction begins with the mitosis of the cell nucleus, followed by the division of the cell itself. Euglena divide longitudinally, beginning at the front end of the cell, with the duplication of flagellar processes, gullet and stigma. Presently, a cleavage forms in the anterior, and a V-shaped bifurcation gradually moves toward the posterior, until the two halves are entirely separated. [21]

Reports of sexual conjugation are rare, and have not been substantiated. [22]

Historical background and early classification

Cercaria viridis (= E. viridis) from O.F. Muller's Animalcula Infusoria. 1786 Mullers cercaria viridis detail.jpg
Cercaria viridis (= E. viridis) from O.F. Müller's Animalcula Infusoria. 1786

Species of Euglena were among the first protists to be seen under the microscope.

In 1674, in a letter to the Royal Society, the Dutch pioneer of microscopy Antonie van Leeuwenhoek wrote that he had collected water samples from an inland lake, in which he found "animalcules" that were "green in the middle, and before and behind white." Clifford Dobell regards it as "almost certain" that these were Euglena viridis, whose "peculiar arrangement of chromatophores...gives the flagellate this appearance at low magnification." [23]

Twenty-two years later, John Harris published a brief series of "Microscopical Observations" reporting that he had examined "a small Drop of the Green Surface of some Puddle-Water" and found it to be "altogether composed of Animals of several Shapes and Magnitudes." Among them, were "oval creatures whose middle part was of a Grass Green, but each end Clear and Transparent," which "would contract and dilate themselves, tumble over and over many times together, and then shoot away like Fish." [24]

In 1786, O.F. Müller gave a more complete description of the organism, which he named Cercaria viridis, noting its distinctive color and changeable body shape. Müller also provided a series of illustrations, accurately depicting the undulating, contractile movements (metaboly) of Euglena's body. [25]

Euglena from Felix Dujardin's Histoire Naturelle des Zoophytes, 1841 Dujardin euglena.jpg
Euglena from Félix Dujardin's Histoire Naturelle des Zoophytes, 1841

In 1830, C. G. Ehrenberg renamed Müller's CercariaEuglena viridis, and placed it, in keeping with the short-lived system of classification he invented, among the Polygastrica in the family Astasiaea: multi-stomached creatures with no alimentary canal, variable body shape but no pseudopods or lorica. [26] [27] By making use of the newly invented achromatic microscope, [28] Ehrenberg was able to see Euglena's eyespot, which he correctly identified as a "rudimentary eye" (although he reasoned, wrongly, that this meant the creature also had a nervous system). This feature was incorporated into Ehrenberg's name for the new genus, constructed from the Greek roots "eu-" (well, good) and glēnē (eyeball, socket of joint). [29]

Ehrenberg did not notice Euglena's flagella, however. The first to publish a record of this feature was Félix Dujardin, who added "filament flagelliforme" to the descriptive criteria of the genus in 1841. [30] Subsequently, the class Flagellata (Cohn, 1853) was created for creatures, like Euglena, possessing one or more flagella. While "Flagellata" has fallen from use as a taxon, the notion of using flagella as a phylogenetic criterion remains vigorous. [31]

Recent phylogeny and classification

Euglenoid movement, known as metaboly Euglenoid movement.jpg
Euglenoid movement, known as metaboly

In 1881, Georg Klebs made a primary taxonomic distinction between green and colorless flagellate organisms, separating photosynthetic from heterotrophic euglenoids. The latter (largely colorless, shape-changing uniflagellates) were divided among the Astasiaceae and the Peranemaceae, while flexible green euglenoids were generally assigned to the genus Euglena. [32]

As early as 1935, it was recognized that this was an artificial grouping, however convenient. [33] In 1948, Pringsheim affirmed that the distinction between green and colorless flagellates had no taxonomic justification, although he acknowledged its practical appeal. He proposed something of a compromise, placing colorless, saprotrophic euglenoids in the genus Astasia, while allowing some colorless euglenoids to share a genus with their photosynthesizing cousins, provided they had structural features that proved common ancestry. Among the green euglenoids themselves, Pringsheim recognized the close kinship of some species of Phacus and Lepocinclis with some species of Euglena. [32]

The idea of classifying the euglenoids by their manner of nourishment was finally abandoned in the 1950s, when A. Hollande published a major revision of the phylum, grouping organisms by shared structural features, such as the number and type of flagella. [34] If any doubt remained, it was dispelled in 1994, when genetic analysis of the non-photosynthesizing euglenoid Astasia longa confirmed that this organism retains sequences of DNA inherited from an ancestor that must have had functioning chloroplasts. [35]

In 1997, a morphological and molecular study of the Euglenozoa put Euglena gracilis in close kinship with the species Khawkinea quartana, with Peranema trichophorum basal to both. [36] Two years later, a molecular analysis showed that E. gracilis was, in fact, more closely related to Astasia longa than to certain other species recognized as Euglena. In 2015, Ellis O'Neill and Professor Rob Field have sequenced the transcriptome of Euglena gracilis, which provides information about all of the genes that the organism is actively using. They found that Euglena gracilis has a whole host of new, unclassified genes which can make new forms of carbohydrates and natural products. [37] [38]

The venerable Euglena viridis was found to be genetically closer to Khawkinea quartana than to the other species of Euglena studied. [34] Recognizing the polyphyletic nature of the genus Euglena, Marin et al. (2003) have revised it to include certain members traditionally placed in Astasia and Khawkinea. [14]

Human consumption

The taste of powdered euglena is described as dried sardine flakes, and contains minerals, vitamins and docosahexaenoic acid, an omega-3 acid. The powder is used as ingredient in other foods. [39] Kemin Industries sells a euglena nutraceutical supplement ingredient featuring dried Euglena gracilis with high levels of beta glucan. [40]

Feedstock for biofuel production

The lipid content of Euglena (mainly wax esters) is seen as a promising feedstock for production of biodiesel and jet fuel. [41] Under the aegis of Itochu, a start-up company called Euglena Co., Ltd. has completed a refinery plant in Yokohama in 2018, with a production capacity of 125 kiloliters of bio jet fuel and biodiesel per year. [42] [43]

Red Euglena sp.
Euglena mutabilis, showing metaboly, paramylon bodies and chloroplasts
Euglena sanguinea
Euglena, moving by metaboly and swimming

See also

Related Research Articles

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

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 15–40 μm (0.00059–0.00157 in) in size, although some euglenids get up to 500 μm (0.020 in) long.

<span class="mw-page-title-main">Flagellate</span> Group of protists with at least one whip-like appendage

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.

<span class="mw-page-title-main">Flagellum</span> Cellular appendage functioning as locomotive or sensory organelle

A flagellum is a hairlike appendage that protrudes from certain plant and animal sperm cells, from fungal spores (zoospores), and from a wide range of microorganisms to provide motility. Many protists with flagella are known as flagellates.

<span class="mw-page-title-main">Euglenid</span> Class of protozoans

Euglenids are one of the best-known groups of flagellates, which are excavate eukaryotes of the phylum Euglenophyta and their cell structure is typical of that group. They are commonly found in freshwater, especially when it is rich in organic materials, with a few marine and endosymbiotic members. Many euglenids feed by phagocytosis, or strictly by diffusion. A monophyletic group consisting of the mixotrophic Rapaza viridis and the two groups Eutreptiales and Euglenales have chloroplasts and produce their own food through photosynthesis. This group is known to contain the carbohydrate paramylon.

<i>Chlamydomonas</i> Genus of algae

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.

Cryptomonas is the name-giving genus of the Cryptomonads established by German biologist Christian Gottfried Ehrenberg in 1831. The algae are common in freshwater habitats and brackish water worldwide and often form blooms in greater depths of lakes. The cells are usually brownish or greenish in color and are characteristic of having a slit-like furrow at the anterior. They are not known to produce any toxins. They are used to feed small zooplankton, which is the food source for small fish in fish farms. Many species of Cryptomonas can only be identified by DNA sequencing. Cryptomonas can be found in several marine ecosystems in Australia and South Korea.

<span class="mw-page-title-main">Paramylon</span> Chemical compound

Paramylon is a carbohydrate similar to starch. The chloroplasts found in Euglena contain chlorophyll which aids in the synthesis of carbohydrates to be stored as starch granules and paramylon. Paramylon is made in the pyrenoids of Euglena. The euglenoids have chlorophylls a and b and they store their photosynthate in an unusual form called paramylon starch, a β-1,3 polymer of glucose. The paramylon is stored in rod like bodies throughout the cytoplasm, called paramylon bodies, which are often visible as colorless or white particles in light microscopy. Their shape is often characteristic of the Euglena species that produces them.

<i>Euglena gracilis</i> Species of single-celled Eukaryote algae

Euglena gracilis is a freshwater species of single-celled alga in the genus Euglena. It has secondary chloroplasts, and is a mixotroph able to feed by photosynthesis or phagocytosis. It has a highly flexible cell surface, allowing it to change shape from a thin cell up to 100 µm long to a sphere of approximately 20 µm. Each cell has two flagella, only one of which emerges from the flagellar pocket (reservoir) in the anterior of the cell, and can move by swimming, or by so-called "euglenoid" movement across surfaces. E. gracilis has been used extensively in the laboratory as a model organism, particularly for studying cell biology and biochemistry.

<i>Tetraselmis</i> Genus of algae

Tetraselmis is a genus of phytoplankton. Tetraselmis is a green algal genus within the order Chlorodendrales, and they are characterized by their intensely-colored green chloroplast, their flagellated cell bodies, the presence of a pyrenoid within the chloroplast, and a scale-produced thecal-wall. Species within this genus are found in both marine and freshwater ecosystems across the globe; their habitat range is mainly limited by water depth due to their photosynthetic nature. Thus, they live in diverse water environments if enough nutrients and light are available for net photosynthetic activity. Tetraselmis species have proven to be useful for both research and industry. Tetraselmis species have been studied for understanding plankton growth rates, and recently a colonial species is being used to gain an understanding of multicellularity evolution. Additionally, many species are currently being examined for their use as biofuels due to their high lipid content.

<i>Trachelomonas</i> Genus of euglenoids

Trachelomonas is a genus of swimming, free-living euglenoids characterized by the presence of a shell-like covering called a lorica. Details of lorica structure determine the classification of distinct species in the genus. The lorica can exist in spherical, elliptical, cylindrical, and pyriform (pear-shaped) forms. The lorica surface can be smooth, punctuate or striate and range from hyaline, to yellow, or brown. These colors are due to the accumulation of ferric hydroxide and manganic oxide deposited with the mucilage and minerals that comprise the lorica. In Trachelomonas, the presence of a lorica obscures cytoplasmic details of the underlying cell. In each Trachelomonas cell, there is a gap at the apex of the lorica from which the flagellum protrudes. Thickening around this gap results in a rim-like or collar-like appearance. During asexual reproduction, the nucleus divides yielding two daughter cells one of which exits through the opening in the lorica. This new cell then synthesizes its own new lorica.

<span class="mw-page-title-main">Eyespot apparatus</span> Photoreceptive organelle

The eyespot apparatus is a photoreceptive organelle found in the flagellate or (motile) cells of green algae and other unicellular photosynthetic organisms such as euglenids. It allows the cells to sense light direction and intensity and respond to it, prompting the organism to either swim towards the light, or away from it. A related response occurs when cells are briefly exposed to high light intensity, causing the cell to stop, briefly swim backwards, then change swimming direction. Eyespot-mediated light perception helps the cells in finding an environment with optimal light conditions for photosynthesis. Eyespots are the simplest and most common "eyes" found in nature, composed of photoreceptors and areas of bright orange-red red pigment granules. Signals relayed from the eyespot photoreceptors result in alteration of the beating pattern of the flagella, generating a phototactic response.

<span class="mw-page-title-main">Euglenales</span> Order of flagellate eukaryotes

Euglenales is an order of flagellates in the phylum Euglenozoa. The family includes the most well-known euglenoid genus, Euglena, as well as other common genera like Phacus and Lepocinclis.

<span class="mw-page-title-main">Euglenaceae</span> Family of flagellate eukaryotes

Euglenaceae is a family of flagellates in the phylum Euglenozoa. The family includes the most well-known euglenoid genus, Euglena.

<i>Phacus</i> Genus of algae

Phacus is a genus of unicellular excavates, of the phylum Euglenozoa, characterized by its flat, leaf-shaped structure, and rigid cytoskeleton known as a pellicle. These eukaryotes are mostly green in colour, and have a single flagellum that extends the length of their body. They are morphologically very flat, rigid, leaf-shaped, and contain many small discoid chloroplasts.

<i>Peranema</i> Genus of protozoans

Peranema is a genus of free-living phagotrophic euglenids. There are more than 20 nominal species, varying in size between 8 and 200 micrometers. Peranema cells are gliding flagellates found in freshwater lakes, ponds and ditches, and are often abundant at the bottom of stagnant pools rich in decaying organic material. Although they belong to the class Euglenoidea, and are morphologically similar to the green Euglena, Peranema have no chloroplasts, and do not conduct autotrophy. Instead, they capture live prey, such as yeast, bacteria and other flagellates, consuming them with the help of a rigid feeding apparatus called a "rod-organ." Unlike the green euglenids, they lack both an eyespot (stigma), and the paraflagellar body (photoreceptor) that is normally coupled with that organelle. However, while Peranema lack a localized photoreceptor, they do possess the light-sensitive protein rhodopsin, and respond to changes in light with a characteristic "curling behaviour."

<i>Euglena viridis</i>

Euglena viridis is a freshwater, single cell, mixotroph microalgae bearing a secondary chloroplast. Their chloroplast is bounded by three layers of membrane without a nucleomorph. Normally, it is 40–65 μm long, slightly bigger than other well-known Euglena species: Euglena gracilis.

Heteronema is a genus of phagotrophic, flagellated euglenoids that are most widely distributed in fresh water environments. This genus consists of two very distinguishable morphogroups that are phylogenetically closely related. These morphogroups are deciphered based on shape, locomotion and other ultrastructural traits. However, this genus does impose taxonomic problems due to the varying historical descriptions of Heteronema species and its similarity to the genus Paranema. The species H. exaratum, was the first heteronemid with a skidding motion to be sequenced, which led to the discovery that it was not closely related to H. scaphrum, contrary to what was previously assumed, but instead to a sister group of primary osmotrophs. This suggests that skidding heteronemids can also be distinguished phylogenetically, being more closely related to Anisoma, Dinema and Aphageae, than to other species within Heteronema.

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.

Cryptoglena(/ˌkɹɪptoʊˈgliːnə/) is a genus of photosynthetic euglenids that was first described in 1831 by Christian Gottfried Ehrenberg. Today, its circumscription is controversial: Bicudo and Menezes consider twenty-one species as Cryptoglena, of which, nine are uncertain. Cryptoglena species are water-based, living in both freshwater and marine environments. They are biflagellated, with one internal flagellum and one external flagellum, which allows movement through environments as demonstrated by Kim and Shin in the species C. pigra. The cells of Cryptoglena resemble a coffee bean, as they have a groove that runs the length of the cell on one side and makes them U-shaped in cross section. They are ovoid in shape and are small, with the larger cells being on average 25 x 15 μm. After being first described in 1831, little work was done on the genus until the late 1970s and early 1980s, after the scanning electron microscope completed development and was implemented into laboratories. Work then proceeded with the developments of molecular biology, which allows for classifications based on DNA sequences. For Cryptoglena the main DNA used for classification are small subunit (SSU) and large subunit (LSU) rDNA.

<span class="mw-page-title-main">Protist locomotion</span> Motion system of a type of eukaryotic organism

Protists are the eukaryotes that cannot be classified as plants, fungi or animals. They are mostly unicellular and microscopic. Many unicellular protists, particularly protozoans, are motile and can generate movement using flagella, cilia or pseudopods. Cells which use flagella for movement are usually referred to as flagellates, cells which use cilia are usually referred to as ciliates, and cells which use pseudopods are usually referred to as amoeba or amoeboids. Other protists are not motile, and consequently have no built-in movement mechanism.

References

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  2. ↑ "The Euglenoid Project for Teachers". The Euglenoid Project for Teachers. Partnerships for Enhancing Expertise in Taxonomy. Archived from the original on February 23, 2017. Retrieved Sep 20, 2014.
  3. ↑ Wolosski, Konrad (2002-04-25). "Phylum Euglenophyta". In John, David M.; Whitton, Brian A.; Brook, Alan J. (eds.). The Freshwater Algal Flora of the British Isles: an Identification Guide to Freshwater and Terrestrial Algae. Cambridge University Press. p. 144. ISBN   978-0-521-77051-4.
  4. ↑ Russell, A. G.; Watanabe, Y; Charette, JM; Gray, MW (2005). "Unusual features of fibrillarin cDNA and gene structure in Euglena gracilis: Evolutionary conservation of core proteins and structural predictions for methylation-guide box C/D snoRNPs throughout the domain Eucarya". Nucleic Acids Research. 33 (9): 2781–91. doi:10.1093/nar/gki574. PMC   1126904 . PMID   15894796.
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  6. ↑ Keeble, Frederick (1912). Plant-animals: a study in symbiosis. London: Cambridge University Press. pp. 103–4. OCLC   297937639.
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  14. 1 2 Marin, B; Palm, A; Klingberg, M; Melkonian, M (2003). "Phylogeny and taxonomic revision of plastid-containing euglenophytes based on SSU rDNA sequence comparisons and synapomorphic signatures in the SSU rRNA secondary structure". Protist. 154 (1): 99–145. doi:10.1078/143446103764928521. PMID   12812373.
  15. ↑ Ciugulea, Ionel; Triemer, Richard (2010). A Color Atlas of Photosynthetic Euglenoids. East Lansing: Michigan State University Press. pp. 17 & 38. ISBN   978-0870138799.
  16. ↑ Häder, Donat-P.; Melkonian, Michael (1983-08-01). "Phototaxis in the gliding flagellate, Euglena mutabilis". Archives of Microbiology. 135 (1): 25–29. doi:10.1007/BF00419477. ISSN   1432-072X. S2CID   19307809.
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  18. ↑ Bouck, G. B.; Rogalski, A.; Valaitis, A. (1978-06-01). "Surface organization and composition of Euglena. II. Flagellar mastigonemes". The Journal of Cell Biology. 77 (3): 805–826. doi:10.1083/jcb.77.3.805. ISSN   0021-9525. PMC   2110158 . PMID   98532.
  19. 1 2 Schaechter, Moselio (2011). Eukaryotic Microbes. San Diego: Elsevier/Academic Press. p. 315. ISBN   978-0-12-383876-6.
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  22. ↑ Lee, John J. (2000). An Illustrated Guide to the Protozoa: organisms traditionally referred to as protozoa, or newly discovered groups. Vol. 2 (2nd ed.). Lawrence, Kansas: Society of Protozoologists. p. 1137.
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  26. ↑ Ehrenberg, C. Organisation, Systematik und geographisches Verhältnifs der Infusionsthierchen. Vol. II. Berlin, 1830. pp 58-9
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  30. ↑ Dujardin, Félix (1841). Histoire Naturelle des Zoophytes. Infusoires, comprenant la Physiologie et la Classification de ces Animaux, et la Manière de les Étudier a l'aide du Microscope. Paris. p. 358.
  31. ↑ Cavalier-Smith, Thomas; Chao, Ema E.-Y. (2003). "Phylogeny and Classification of Phylum Cercozoa (Protozoa)". Protist. 154 (3–4): 341–58. doi:10.1078/143446103322454112. PMID   14658494. S2CID   26079642.
  32. 1 2 Pringsheim, E. G. (1948). "Taxonomic Problems in the Euglenineae". Biological Reviews. 23 (1): 46–61. doi:10.1111/j.1469-185X.1948.tb00456.x. PMID   18901101. S2CID   33439406.
  33. ↑ Schwartz, Adelheid (2007). "F. E. Fritsch, the Structure and Reproduction of the Algae Vol. I/II. XIII und 791, XIV und 939 S., 245 und 336 Abb., 2 und 2 Karten. Cambridge 1965 (reprinted): Cambridge University Press 90 S je Band". Zeitschrift für Allgemeine Mikrobiologie. 7 (2): 168–9. doi:10.1002/jobm.19670070220.
  34. 1 2 Linton, Eric W.; Hittner, Dana; Lewandowski, Carole; Auld, Theresa; Triemer, Richard E. (1999). "A Molecular Study of Euglenoid Phylogeny using Small Subunit rDNA". The Journal of Eukaryotic Microbiology. 46 (2): 217–23. doi:10.1111/j.1550-7408.1999.tb04606.x. PMID   10361741. S2CID   31420687.
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  37. ↑ The potential in your pond published on August 14, 2015 by the "John Innes Centre"
  38. ↑ O'Neill, Ellis C.; Trick, Martin; Hill, Lionel; Rejzek, Martin; Dusi, Renata G.; Hamilton, Christopher J.; Zimba, Paul V.; Henrissat, Bernard; Field, Robert A. (2015). "The transcriptome of Euglena gracilis reveals unexpected metabolic capabilities for carbohydrate and natural product biochemistry". Molecular BioSystems. 11 (10): 2808–21. doi: 10.1039/C5MB00319A . PMID   26289754.
  39. ↑ "Tiny euglena latest fad in eating healthy". The Japan Times. 23 January 2014.
  40. ↑ "BetaVia™". Kemin. Retrieved 2021-09-16.
  41. ↑ Toyama, Tadashi; Hanaoka, Tsubasa (2019). "Enhanced production of biomass and lipids by Euglena gracilis via co-culturing with a microalga growth-promoting bacterium". Biotechnology for Biofuels. 12: 205. doi: 10.1186/s13068-019-1544-2 . PMC   6822413 . PMID   31695747.
  42. ↑ Okutsu, Akane (2018). "Biotech company euglena teams with ANA to fuel green commercial flights". Nikkei (published November 2, 2018). Retrieved April 8, 2020.
  43. ↑ Video explanation lacks technical details but suggests degree of government commitment to solving problems of large-scale cultivation and infrastructure. CEO of Euglena Co. wears euglena-green necktie. "Fueling Jet Aircraft With Microalgae: Growing biofuel without farmlands". JapanGov. The Government of Japan. Retrieved April 8, 2020.
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