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== Ecology ==
== Ecology ==


Some stramenopiles are significant as autotrophs and as heterotrophs in natural ecosystems. ''[[Blastocystis]]'' is a parasite of humans; opalines and proteromonads live in the intestines of cold-blooded vertebrates; oomycetes include some significant plant pathogens (including the agent that caused the potato blight famine in Ireland that resulted in approximately one million deaths and led to extensive emigration). Diatoms are major contributors to global carbon cycles because they are the most important autotrophs in most marine habitats. The brown algae (or kelp) are major autotrophs of the intertidal and subtidal marine habitats. Some of the bacterivorous stramenopiles, such as ''[[Cafeteria (bicosoecid)|Cafeteria]]'' are common and widespread consumers of bacteria, and thus play a major role in recycling carbon and nutrients within [[microbial food web]]s.{{citation needed|date=March 2023}}
Some stramenopiles are significant as autotrophs and as heterotrophs in natural ecosystems.
''[[Blastocystis]]'' is a parasite of humans;<ref name="Roberts Stark Harkness Ellis 2014 p=17">{{cite journal |last=Roberts |first=Tamalee |last2=Stark |first2=Damien |last3=Harkness |first3=John |last4=Ellis |first4=John |title=Update on the pathogenic potential and treatment options for Blastocystis sp |journal=Gut Pathogens |volume=6 |issue=1 |year=2014 |doi=10.1186/1757-4749-6-17 |page=17}}</ref>
opalines and proteromonads live in the intestines of cold-blooded vertebrates;
oomycetes include some significant plant pathogens (including the agent that caused the potato blight famine in Ireland that resulted in approximately one million deaths and led to extensive emigration).
Diatoms are major contributors to global carbon cycles because they are the most important autotrophs in most marine habitats.
The brown algae (or kelp) are major autotrophs of the intertidal and subtidal marine habitats.
Some of the bacterivorous stramenopiles, such as ''[[Cafeteria (bicosoecid)|Cafeteria]]'' are common and widespread consumers of bacteria, and thus play a major role in recycling carbon and nutrients within [[microbial food web]]s.{{citation needed|date=March 2023}}


== Phylogeny ==
== Phylogeny ==

Revision as of 11:07, 17 March 2023

Stramenopile
Ochromonas sp. (Chrysophyceae), with two unequal (heterokont) flagella. Mastigonemes not represented.
Ochromonas sp. (Chrysophyceae), with two unequal (heterokont) flagella. Mastigonemes not represented.
Scientific classification Edit this classification
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Stramenopiles
Phyla and subphyla[1]
Synonyms

Stramenopile is 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 (in which case relatedness to stramenopile ancestors is evident from other shared cytological features or from genetic similarity). Stramenopiles represent one of the three major clades in the SAR supergroup, along with Alveolata and Rhizaria.

Members of the clade are referred to as 'stramenopiles'. Stramenopiles are eukaryotes; since they are neither fungi, animals, nor plants, they are classified as protists. Most stramenopiles are single-celled, but some are multicellular algae including some brown algae. The group includes a variety of algal protists, heterotrophic flagellates, opalines and closely related proteromonad flagellates (all endobionts in other organisms); the actinophryid heliozoa, and oomycetes. The tripartite hairs have been lost in some stramenopiles - for example in most diatoms (although these organisms still express mastigonemic proteins - see below).

Many stramenopiles are unicellular flagellates, and most others produce flagellated cells at some point in their lifecycles, for instance as gametes or zoospores. Most flagellated heterokonts have two flagella; the anterior flagellum has one or two rows of stiff hairs or mastigonemes, and the posterior flagellum is without such embellishments, being smooth, usually shorter, or in a few cases not projecting from the cell.

History

The term 'Stramenopile' was introduced by D. J. Patterson in 1989, defining a group that overlapped with the ambiguously defined heterokonts.[10] The name "stramenopile" has been discussed by J. C. David.[11]

The heterokont problem

The term 'heterokont' is used as both an adjective – indicating that a cell has two dissimilar flagella – and as the name of a taxon. The taxon 'Heterokontae' was introduced in 1899 by Alexander Luther for algae that are now considered the Xanthophyceae.[12] But the same term was used for other groupings of algae. For example, in 1956, Copeland[13] used it to include the xanthophytes (using the name Vaucheriacea), a group that included what became known as the chrysophytes, the silicoflagellates, and the hyphochytrids. Copeland also included the unrelated collar flagellates (as the choanoflagellates) in which he placed the bicosoecids. He also included the not-closely-related haptophytes. The consequence of associating multiple concepts to the taxon 'heterokont' is that the meaning of 'heterokont' can only be made clear by making reference to its usage: Heterokontae sensu Luther 1899; Heterokontae sensu Copeland 1956, etc. This contextual clarification is rare, such that when the taxon name is used, it is unclear how it should be understood. The term 'Heterokont' has lost its usefulness in critical discussions about the identity, nature, character and relatedness of the group.[14] The term 'stramenopile' sought to identify a clade (monophyletic and holophyletic lineage) using the approach developed by transformed cladists of pointing to a defining innovative characteristic or apomorphy.[15]

Over time, the scope of application has changed, especially when in the 1970s ultrastructural studies revealed greater diversity among the algae with chromoplasts (chlorophylls a and c) than had previously been recognized. At the same time, a protistological perspective was replacing the 19th century one based on the division of unicellular eukaryotes into animals and plants. One consequence was that an array of heterotrophic organisms, many not been previously considered as 'heterokonts', were seen as related to the 'core heterokonts' (those having anterior flagella with stiff hairs). Newly recognized relatives included the parasitic opalines, proteromonads, and actinophryid heliozoa. They joined other heterotrophic protists, such as bicosoecids, labyrinthulids, and oomycete fungi, that were included by some as heterokonts and excluded by others. Rather than continue to use a name whose meaning had changed over time and was hence ambiguous, the name 'stramenopile' was introduced to refer to the clade of protists that had tripartite stiff (usually flagellar) hairs and all their descendents. Molecular studies confirm that the genes that code for the proteins of these hairs are exclusive to stramenopiles.[16]

Characteristics

Schematic drawing of Cafeteria roenbergensis (a heterotrophic bicosoecid), a common bacterivore in marine ecosystems: the anterior flagellum is tripartite and covered with hairs (mastigonemes); the posterior flagellum is without hairs.
Two living C. roenbergensis. Light micrograph. The cells are about 6 µm long. The anterior flagellum beats with an undulating pattern, the posterior (recurrent or smooth) flagellum usually holds the cell to the substrate.

The presumed apomorphy of tripartite flagellar hairs in stramenopiles is well characterized. The basal part of the hair is flexible and inserts into the cell membrane; the second part is dominated by a long stiff tube (the 'straw' or 'stramen'); and finally the tube is tipped by many delicate hairs called mastigonemes.[17] The proteins that code for the mastigonemes appear to be exclusive to the stramenopile clade, and are present even in taxa (such as diatoms) that no longer have such hairs.[18]

Most stramenopiles have two flagella that insert subapically or laterally. They are usually supported by four microtubule roots in a distinctive pattern. There is a transitional helix inside the flagellum where the beating axoneme with its distinctive 9 peripheral couplets and two central microtubules changes into the nine triplet structure of the basal body.[citation needed]

Plastids

Many stramenopiles have plastids which enable them to photosynthesise, using light to make their own food. Those plastids are coloured off-green, orange, golden or brown because of the presence of chlorophyll a, chlorophyll c, and fucoxanthin. This form of plastid is called a stramenochrome or chromoplast.[a] The most significant autotrophic stramenopiles are the brown algae (wracks and many other seaweeds), and the diatoms. The latter are among the most significant primary producers in marine and freshwater ecosystems.[19]

Chromoplasts are surrounded by four membranes. The outermost is continuous with the chloroplast endoplasmic reticulum. The second membrane presents a barrier between the lumen of the chloroplast endoplasmic reticulum and the primary endosymbiont or chloroplast. The two innermost membranes, and the photosynthetic thylakoids that they surround, represent the symbiont, a unicellular red alga effectively captured by the stramenopile.

Most molecular analyses suggest that the most basal stramenopiles lacked plastids and were accordingly colourless heterotrophs, feeding on other organisms. This implies that the stramenopiles arose as heterotrophs, diversified, and then some of them acquired chromoplasts. Some lineages (such as the axodine lineage that included the chromophytic pedinellids, colourless ciliophryids, and colourless actinophryid heliozoa) have secondarily reverted to heterotrophy.[20][21]

Ecology

Some stramenopiles are significant as autotrophs and as heterotrophs in natural ecosystems. Blastocystis is a parasite of humans;[22] opalines and proteromonads live in the intestines of cold-blooded vertebrates; oomycetes include some significant plant pathogens (including the agent that caused the potato blight famine in Ireland that resulted in approximately one million deaths and led to extensive emigration). Diatoms are major contributors to global carbon cycles because they are the most important autotrophs in most marine habitats. The brown algae (or kelp) are major autotrophs of the intertidal and subtidal marine habitats. Some of the bacterivorous stramenopiles, such as Cafeteria are common and widespread consumers of bacteria, and thus play a major role in recycling carbon and nutrients within microbial food webs.[citation needed]

Phylogeny

External

In terms of relatedness among protists, Krylov and co-workers proposed that the morphology of mitochondrial cristae remained relatively unchanged over time, and would define large sectors of protistan diversity.[23] Subsequent molecular studies have confirmed this, showing that the Stramenopiles are most closely related to Alveolates and Rhizaria - all with tubular mitochondrial cristae and collectively forming the SAR supergroup, whose name is formed from their initials.[21][24]

SAR supergroup

Rhizaria

Halvaria

Stramenopiles

Alveolata

Internal

The tree is based on Ruggiero et al. 2015 & Silar 2016.[25][26][27]

Stramenopiles

Platysulcidae Shiratori, Nkayama & Ishida 2015

Bikosea Cavalier-Smith 2013

Placidozoa

Placididea Moriya, Nakayama & Inouye 2002

Nanomonadea Cavalier-Smith 2013

Opalomonadea Cavalier-Smith 2013

Opalinata

Blastocystea Zierdt et al. 1967

Opalinea Wenyon 1926 emend. Cavalier-Smith 1993

Gyrista

Bigyromonadea Cavalier-Smith 1998

Oomycota Arx 1967

Hyphochytriomycota Whittaker 1969

Pirsoniales Cavalier-Smith 1998

Ochrophyta
Khakista

Bolidophyceae Guillou & Chretiennot-Dinet 1999

Bacillariophyceae Haeckel 1878

Phaeista
Hypogyristea s.s.

Dictyochophyceae Silva 1980 s.l.

Chrysista
Eustigmista

Pinguiophyceae Kawachi et al. 2002

Eustigmatophyceae Hibberd & Leedale 1971

Phagochrysia

Picophagea Cavalier-Smith 2006

Synchromophyceae Horn & Wilhelm 2007

Leukarachnion Geitler 1942

Chrysophyceae Pascher 1914

Xanthophytina
Raphidoistia

Raphidophyceae s.l.

Fucistia

Phaeophyceae Hansgirg 1886

Chrysomerophyceae Cavalier-Smith 1995

Phaeothamniophyceae Andersen & Bailey 1998 s.l.

Xanthophyceae Allorge 1930 emend. Fritsch 1935

(Heterokonts)

Classification

Electron micrograph of the protist Paraphysomonas butcheri. It illustrates the stramenopile property - of having stiff hairs. The hairs attach to one longer flagellum, the other is without hairs (an arrangement also called 'heterokont', meaning "unequal"). The body of the flagellate is coated with delicate scales. Paraphysomonas feeds on bacteria, two of which lie near the hairy flagellum.

The classification of the Stramenopiles according to Adl et al. (2012) is:[28]

Notes

  1. ^ They are not called chloroplasts, the most common form of photosynthetic plastid. If used narrowly, a chloroplast is a plastid which contains chlorophyll B, as in green algae, some euglenids, and the land plants.

References

  1. ^ Cavalier-Smith, Thomas (2017). "Kingdom Chromista and its eight phyla: a new synthesis emphasising periplastid protein targeting, cytoskeletal and periplastid evolution, and ancient divergences". Protoplasma. 255 (1): 297–357. doi:10.1007/s00709-017-1147-3. PMC 5756292. PMID 28875267.
  2. ^ Patterson, D.J. (1989). "Stramenopiles: Chromophytes from a protistan perspective". In Green, J.C.; Leadbeater, B.S.C.; Diver, W.L. (eds.). The chromophyte algae: Problems and perspectives. Clarendon Press. ISBN 978-0198577133.
  3. ^ Vørs, N (1993). "Marine heterotrophic amoebae, flagellates and heliozoa from Belize (Central America) and Tenerife". Journal of Eukaryotic Microbiology. 40 (3): 272–287. doi:10.1111/j.1550-7408.1993.tb04917.x. S2CID 221852241.
  4. ^ David, J.C. (2002). "A preliminary catalogue of the names of fungi above the rank of order". Constancea. 83: 1–30.
  5. ^ Cavalier-Smith, T. (1999). "The kingdom Chromista, origin and systematics". In Round, F.E.; Chapman, D.J. (eds.). Progress in Phycological Research. Vol. 4. Elsevier. pp. 309–347. ISBN 978-0-948737-00-8.
  6. ^ van den Hoek, C.; Mann, D.G.; Jahns, H.M. (1995). Algae An Introduction to Phycology. Cambridge University Press. ISBN 978-0-521-30419-1.
  7. ^ Alexopoulos, C.J.; Mims, C.W.; Blackwell, M. (1996). Introductory Mycology (4th ed.). Wiley. ISBN 978-0471522294.
  8. ^ Dick, M.W. (2013). Straminipilous Fungi: Systematics of the Peronosporomycetes Including Accounts of the Marine Straminipilous Protists, the Plasmodiophorids and Similar Organisms. Springer. ISBN 978-94-015-9733-3.
  9. ^ "Stramenipila M.W. Dick (2001)". MycoBank. International Mycological Association.
  10. ^ Patterson, D. J. (1989). "Stramenopiles: chromophytes from a protistological perspective". In Green, J. C.; Leadbeater, B. S. C.; Diver, W. L. (eds.). The chromophyte algae: problems and perspectives. Oxford: Clarendon Press. pp. 357–379.
  11. ^ David, J. C. (2002). "A preliminary catalogue of the names of fungi above the rank of order". Constancea (83): 1–30.
  12. ^ Luther, Alexander F. (1899). Über Chlorosaccus eine neue Gattung der Süsswasseralgen nebst einiger Bemerkungen zur Systematik verwandter Algen [About Chlorosaccus a new genus of freshwater algae together with some comments on the systematics of related algae] (in German). Stockholm: Norstedt. pp. 1–22.
  13. ^ Copeland, H. F. (1956). The Classification of Lower Organisms. Palo Alto, California: Pacific Books.
  14. ^ Blackwell, W. H. (2009). "Chromista revisited: A dilemma of overlapping putative kingdoms, and the attempted application of the botanical code of nomenclature" (PDF). Phytologia. 91 (2).
  15. ^ Patterson, Colin (1982). "Morphological characters and homology". In Joysey, Kenneth A.; Friday, A. E. (eds.). Problems in Phylogenetic Reconstruction. Systematics Association Special Volume 21. London: Academic Press. ISBN 978-0-1239-1250-3.
  16. ^ Hee, Wei Yih; Blackman, Leila M.; Hardham, Adrienne R. (2019). "Characterisation of Stramenopile-specific mastigoneme proteins in Phytophthora parasitica". Protoplasma. 256 (2): 521–535. doi:10.1007/s00709-018-1314-1. PMID 30302550. S2CID 52947780.
  17. ^ Bouck, G. Benjamin (1 August 1971). "The structure, origin, and composition of the tubular mastigonemes of the Ochromonas flagellum". Journal of Cell Biology. 50 (2): 362–384. doi:10.1083/jcb.50.2.362.
  18. ^ Blackman, Leila M.; Arikawa, Mikihiko; Yamada, Shuhei; Suzaki, Toshinobu; Hardham, Adrienne R. (2011). "Identification of a Mastigoneme Protein from Phytophthora nicotianae". Protist. 162 (1): 100–114. doi:10.1016/j.protis.2010.01.005.
  19. ^ Leipe, D. D.; Wainright, P. O.; Gunderson, J. H.; et al. (1994). "The stramenopiles from a molecular perspective: 16S-like rRNA sequences from Labyrinthuloides minuta and Cafeteria roenbergensis". Phycologia. 33 (5): 369–377. doi:10.2216/i0031-8884-33-5-369.1.
  20. ^ Leyland, Ben; Leu, Stefan; Boussiba, Sammy (2017). "Are Thraustochytrids algae?". Fungal Biology. 121 (10): 835–840. doi:10.1016/j.funbio.2017.07.006.
  21. ^ a b Derelle, Romain; López-García, Purificación; Timpano, Hélène; Moreira, David (10 August 2016). "A Phylogenomic Framework to Study the Diversity and Evolution of Stramenopiles (=Heterokonts)". Molecular Biology and Evolution. 33 (11): 2890–2898. doi:10.1093/molbev/msw168.
  22. ^ Roberts, Tamalee; Stark, Damien; Harkness, John; Ellis, John (2014). "Update on the pathogenic potential and treatment options for Blastocystis sp". Gut Pathogens. 6 (1): 17. doi:10.1186/1757-4749-6-17.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  23. ^ Krylov, M. V.; Dobrovolskii, A. A.; Issi, I. V.; Michaelevich, B. I.; Podlipaev, S. A.; Reshetnyak, V. V.; Seravin, L. N.; et al. 1980. New concepts for the system of unicellular organisms. Trudy Zoologischkei Institut Akademiya Nayuk, SSSR 94:122–132.
  24. ^ Burki, F.; Shalchian-Tabrizi; Pawlowski, J. (August 2008). "Phylogenomics reveals a new 'megagroup' including most photosynthetic eukaryotes". Biology Letters. 4 (4): 366–369. doi:10.1098/rsbl.2008.0224. PMC 2610160. PMID 18522922.
  25. ^ Ruggiero; et al. (2015). "Higher Level Classification of All Living Organisms". PLOS ONE. 10 (4): e0119248. Bibcode:2015PLoSO..1019248R. doi:10.1371/journal.pone.0119248. PMC 4418965. PMID 25923521.
  26. ^ Silar, Philippe (2016). "Protistes Eucaryotes: Origine, Evolution et Biologie des Microbes Eucaryotes". HAL Archives-ouvertes: 1–462.
  27. ^ Cavalier-Smith, Thomas; Scoble, Josephine Margaret (2013). "Phylogeny of Heterokonta: Incisomonas marina, a uniciliate gliding opalozoan related to Solenicola (Nanomonadea), and evidence that Actinophryida evolved from raphidophytes". European Journal of Protistology. 49 (3): 328–353. doi:10.1016/j.ejop.2012.09.002. PMID 23219323.
  28. ^ Adl, Sina M.; Simpson, Alastair G. B.; Lane, Christopher E.; et al. (2012). "The Revised Classification of Eukaryotes". Journal of Eukaryotic Microbiology. 59 (5): 429–514. doi:10.1111/j.1550-7408.2012.00644.x. PMC 3483872. PMID 23020233.
  29. ^ Graf, Louis; Yoon, Hwan Su (21 July 2021). "Olisthodiscophyceae, the 17th heterokont algal class". Journal of Phycology. 57 (4): 1091–1093. doi:10.1111/jpy.13184. PMID 34289104. S2CID 236175098.
  30. ^ Barcytė, Dovilė; Eikrem, Wenche; Engesmo, Anette; Seoane, Sergio; Wohlmann, Jens; Horák, Aleš; Yurchenko, Tatiana; Eliáš, Marek (2 March 2021). "Olisthodiscus represents a new class of Ochrophyta". Journal of Phycology. 57 (4): 1094–1118. doi:10.1111/jpy.13155. hdl:10852/86515. PMID 33655496. S2CID 232101186.

External links

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