Oomycetes were originally grouped with fungi due to similarities in morphology and lifestyle. However, molecular and phylogenetic studies revealed significant differences between fungi and oomycetes which means the latter are now grouped with the stramenopiles (which include some types of algae). The Oomycota have a very sparse fossil record; a possible oomycete has been described from Cretaceousamber.[7]
Oomycota comes from the Greek ωόν (oon, 'egg') and μύκητας (mykitas, 'fungus'),[8][9] referring to the large round oogonia, structures containing the female gametes, that are characteristic of the oomycetes.
The name "water mold" refers to their earlier classification as fungi and their preference for conditions of high humidity and running surface water, which is characteristic for the basal taxa of the oomycetes.
Morphology
The oomycetes rarely have septa (see hypha), and if they do, they are scarce,[10] appearing at the bases of sporangia, and sometimes in older parts of the filaments.[11] Some are unicellular, while others are filamentous and branching.[11]
Previously the group was arranged into six orders.[11]
The Saprolegniales are the most widespread. Many break down decaying matter; others are parasites.
The Leptomitales have wall thickenings that give their continuous cell body the appearance of septation. They bear chitin and often reproduce asexually.
The Rhipidiales use rhizoids to attach their thallus to the bed of stagnant or polluted water bodies.
The Albuginales are considered by some authors to be a family (Albuginaceae) within the Peronosporales, although it has been shown that they are phylogenetically distinct from this order.
The Peronosporales too are mainly saprophytic or parasitic on plants, and have an aseptate, branching form. Many of the most damaging agricultural parasites belong to this order.
The Lagenidiales are the most primitive; some are filamentous, others unicellular; they are generally parasitic.
However more recently this has been expanded considerably.[12][13]
This group was originally classified among the fungi (the name "oomycota" means "egg fungus") and later treated as protists, based on general morphology and lifestyle.[7] A cladistic analysis based on modern discoveries about the biology of these organisms supports a relatively close relationship with some photosynthetic organisms, such as brown algae and diatoms. A common taxonomic classification based on these data, places the class Oomycota along with other classes such as Phaeophyceae (brown algae) within the phylumHeterokonta.
This relationship is supported by a number of observed differences between the characteristics of oomycetes and fungi. For instance, the cell walls of oomycetes are composed of cellulose rather than chitin[14] and generally do not have septations. Also, in the vegetative state they have diploid nuclei, whereas fungi have haploid nuclei. Most oomycetes produce self-motile zoospores with two flagella. One flagellum has a "whiplash" morphology, and the other a branched "tinsel" morphology. The "tinsel" flagellum is unique to the Kingdom Heterokonta. Spores of the few fungal groups which retain flagella (such as the Chytridiomycetes) have only one whiplash flagellum.[14] Oomycota and fungi have different metabolic pathways for synthesizing lysine and have a number of enzymes that differ.[14] The ultrastructure is also different, with oomycota having tubular mitochondrial cristae and fungi having flattened cristae.[14]
In spite of this, many species of oomycetes are still described or listed as types of fungi and may sometimes be referred to as pseudofungi, or lower fungi.
Most of the oomycetes produce two distinct types of spores. The main dispersive spores are asexual, self-motile spores called zoospores, which are capable of chemotaxis (movement toward or away from a chemical signal, such as those released by potential food sources) in surface water (including precipitation on plant surfaces). A few oomycetes produce aerial asexual spores that are distributed by wind. They also produce sexual spores, called oospores, that are translucent, double-walled, spherical structures used to survive adverse environmental conditions.
Ecology and pathogenicity
Unidentified water mold on dead larval mayfly.
A culture of Achlya sp. (Saprolegniales) isolated from a stream.
Many oomycetes species are economically important, aggressive algae and plant pathogens.[15][16] Some species can cause disease in fish, and at least one is a pathogen of mammals. The majority of the plant pathogenic species can be classified into four groups, although more exist.
The paraphyleticPythium group is more prevalent than Phytophthora and individual species have larger host ranges, although usually causing less damage. Pythiumdamping off is a very common problem in greenhouses, where the organism kills newly emerged seedlings. Mycoparasitic members of this group (e.g. P. oligandrum) parasitize other oomycetes and fungi, and have been employed as biocontrol agents. One Pythium species, Pythium insidiosum, also causes Pythiosis in mammals.
The third group are the downy mildews, which are easily identifiable by the appearance of white, brownish or olive "mildew" on the leaf undersides (although this group can be confused with the unrelated fungal powdery mildews).
The fourth group are the white blister rusts, Albuginales, which cause white blister disease on a variety of flowering plants. White blister rusts sporulate beneath the epidermis of their hosts, causing spore-filled blisters on stems, leaves and the inflorescence. The Albuginales are currently divided into three genera, Albugo parasitic predominantly to Brassicales, Pustula, parasitic predominantly to Asterales, and Wilsoniana, predominantly parasitic to Caryophyllales. Like the downy mildews, the white blister rusts are obligate biotrophs, which means that they are unable to survive without the presence of a living host.
^ abAgrios, George (2005). Plant Pathology. Elsevier. p. 409.
^Vallance, J.; Le Floch, G.; Deniel, F.; Barbier, G.; Levesque, C. A.; Rey, P. (2009). "Influence of Pythium oligandrum Biocontrol on Fungal and Oomycete Population Dynamics in the Rhizosphere". Applied and Environmental Microbiology. 75 (14): 4790–800. Bibcode:2009ApEnM..75.4790V. doi:10.1128/AEM.02643-08. PMC2708430. PMID 19447961.
^ ab"Introduction to the Oomycota". Retrieved 2014-07-07.
^Kortekamp, A. (2005). "Growth, occurrence and development of septa in Plasmopara viticola and other members of the Peronosporaceae using light- and epifluorescence-microscopy". Mycological Research. 109 (Pt 5): 640–648. doi:10.1017/S0953756205002418. PMID 16018320.
^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, PMC4418965, PMID 25923521
^Silar, Philippe (2016), "Protistes Eucaryotes: Origine, Evolution et Biologie des Microbes Eucaryotes", HAL Archives-ouvertes: 1–462
^ abcdVan der Auwera G, De Baere R, Van de Peer Y, De Rijk P, Van den Broeck I, De Wachter R (July 1995). "The phylogeny of the Hyphochytriomycota as deduced from ribosomal RNA sequences of Hyphochytrium catenoides". Mol. Biol. Evol. 12 (4): 671–8. doi:10.1093/oxfordjournals.molbev.a040245. PMID 7659021.
^Agrios, George N. (2005). Plant Pathology. 5th ed. Academic Press. link.
^Schwelm A, Badstöber J, Bulman S, Desoignies N, Etemadi M, Falloon RE, Gachon CM, Legreve A, Lukeš J, Merz U, Nenarokova A, Strittmatter M, Sullivan BK, Neuhauser S (April 2018). "Not in your usual Top 10: protists that infect plants and algae". Molecular Plant Pathology. 19 (4): 1029–1044. doi:10.1111/mpp.12580. PMC5772912. PMID 29024322.
^Haas, BJ; Kamoun, S; Zody, MC; Jiang, RH; Handsaker, RE; Cano, LM; Grabherr, M; Kodira, CD; et al. (2009). "Genome sequence and analysis of the Irish potato famine pathogen Phytophthora infestans". Nature. 461 (7262): 393–8. Bibcode:2009Natur.461..393H. doi:10.1038/nature08358. PMID 19741609.
^Vettraino, A. M.; Morel, O.; Perlerou, C.; Robin, C.; Diamandis, S.; Vannini, A. (2005). "Occurrence and distribution of Phytophthora species in European chestnut stands, and their association with Ink Disease and crown decline". European Journal of Plant Pathology. 111 (2): 169–180. doi:10.1007/s10658-004-1882-0. S2CID 2041934.
External links
Description of The Phylum Oomycota – Systematic Biology
Introduction to the Oomycota – University of California Museum of Paleontology (UCMP)
Genome sequence and analysis of the Irish potato famine pathogen Phytophthora infestans
January 31, 2023
oomycete, oomycota, forms, distinct, phylogenetic, lineage, fungus, like, eukaryotic, microorganisms, called, oomycetes, they, filamentous, heterotrophic, reproduce, both, sexually, asexually, sexual, reproduction, oospore, result, contact, between, hyphae, ma. Oomycota forms a distinct phylogenetic lineage of fungus like eukaryotic microorganisms called oomycetes ˌ oʊ e ˈ m aɪ s iː t s 4 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 5 Asexual reproduction involves the formation of chlamydospores and sporangia producing motile zoospores 5 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 6 The oomycetes are also often referred to as water molds or water moulds although the water preferring nature which led to that name is not true of most species which are terrestrial pathogens OomycetesAsexual A sporangia B zoospores C chlamydospores and sexual D oospores reproductive structures of Phytophthora infestans Peronosporales Scientific classificationKingdom ChromistaSuperphylum HeterokontaPhylum GyristaSubphylum PseudofungiArx 1967 1 Class OomycetesG Winter 1880Orders and familiesDiatomophthoraceae Miraculaceae Lagenidiales Lagenidiaceae Olpidiosidaceae Sirolpidiaceae Leptomitales Leptomitaceae Peronosporales Albuginaceae Peronosporaceae Pythiaceae Rhipidiales Rhipidaceae Saprolegniales Ectrogellaceae Haliphthoraceae Leptolegniellaceae SaprolegniaceaeSynonymsOomycetes Winter 1879 2 Peronosporomycetes Dick 2001 3 Oomycetes were originally grouped with fungi due to similarities in morphology and lifestyle However molecular and phylogenetic studies revealed significant differences between fungi and oomycetes which means the latter are now grouped with the stramenopiles which include some types of algae The Oomycota have a very sparse fossil record a possible oomycete has been described from Cretaceous amber 7 Contents 1 Etymology 2 Morphology 3 Classification 4 Phylogenetic relationships 4 1 Internal 4 2 External 5 Biology 5 1 Reproduction 5 2 Ecology and pathogenicity 6 References 7 External linksEtymology EditOomycota comes from the Greek won oon egg and mykhtas mykitas fungus 8 9 referring to the large round oogonia structures containing the female gametes that are characteristic of the oomycetes The name water mold refers to their earlier classification as fungi and their preference for conditions of high humidity and running surface water which is characteristic for the basal taxa of the oomycetes Morphology EditThe oomycetes rarely have septa see hypha and if they do they are scarce 10 appearing at the bases of sporangia and sometimes in older parts of the filaments 11 Some are unicellular while others are filamentous and branching 11 Classification Edit Simplified phylogeny Asexual structures sporangia in Saprolegniales Albuginales and Peronosporales Sexual structures only oogonia antheridia not shown of Saprolegnia Previously the group was arranged into six orders 11 The Saprolegniales are the most widespread Many break down decaying matter others are parasites The Leptomitales have wall thickenings that give their continuous cell body the appearance of septation They bear chitin and often reproduce asexually The Rhipidiales use rhizoids to attach their thallus to the bed of stagnant or polluted water bodies The Albuginales are considered by some authors to be a family Albuginaceae within the Peronosporales although it has been shown that they are phylogenetically distinct from this order The Peronosporales too are mainly saprophytic or parasitic on plants and have an aseptate branching form Many of the most damaging agricultural parasites belong to this order The Lagenidiales are the most primitive some are filamentous others unicellular they are generally parasitic However more recently this has been expanded considerably 12 13 Anisolpidiales Dick 2001 Anisolpidiaceae Karling 1943 Lagenismatales Dick 2001 Lagenismataceae Dick 1995 Salilagenidiales Dick 2001 Salilagenidiaceae Dick 1995 Rozellopsidales Dick 2001 Rozellopsidaceae Dick 1995 Pseudosphaeritaceae Dick 1995 Ectrogellales Ectrogellaceae Haptoglossales Haptoglossaceae Eurychasmales Eurychasmataceae Petersen 1905 Haliphthorales Haliphthoraceae Vishniac 1958 Olpidiopsidales Sirolpidiaceae Cejp 1959 Pontismataceae Petersen 1909 contains Petersenia Sparrow 1934 Pontisma H E Petersen 1905 Olpidiopsidaceae Cejp 1959 Atkinsiellales Atkinisellaceae Crypticolaceae Dick 1995 Saprolegniales Achlyaceae Verrucalvaceae Dick 1984 Saprolegniaceae Warm 1884 Leptolegniaceae Leptomitales Leptomitaceae Kuetz 1843 Apodachlyellaceae Dick 1986 Leptolegniellaceae Dick 1971 Ducellieriaceae Dick 1995 Rhipidiales Rhipidiaceae Cejp 1959 Albuginales Albuginaceae Schroet 1893 Peronosporales Pythiales Sclerosporales Lagenidiales Salisapiliaceae Pythiaceae Schroet 1893 Pythiogetonaceae Lagenaceae Dick 1994 Lagenidiaceae Peronophythoraceae Myzocytiopsidaceae Dick 1995 Peronosporaceae Warm 1884 Sclerosporaceae Dick 1984 Phylogenetic relationships Edit Pythium sp Peronosporales which causes pythiosis in animals under microscope Symptom of late blight P infestans Peronosporales on the underside of a potato leaf Albugo candida Albuginales on shepherd s purse Capsella bursa pastoris Brassicales Internal Edit HaptoglossalesEurychasmalesHaliphthoralesOlpidiopsidalesOogametia Saprolegniomycetes AtkinsiellalesSaprolegnialesLeptomitalesPeronosporomycetes s s RhipidialesAlbuginalesPeronosporalesExternal Edit This group was originally classified among the fungi the name oomycota means egg fungus and later treated as protists based on general morphology and lifestyle 7 A cladistic analysis based on modern discoveries about the biology of these organisms supports a relatively close relationship with some photosynthetic organisms such as brown algae and diatoms A common taxonomic classification based on these data places the class Oomycota along with other classes such as Phaeophyceae brown algae within the phylum Heterokonta This relationship is supported by a number of observed differences between the characteristics of oomycetes and fungi For instance the cell walls of oomycetes are composed of cellulose rather than chitin 14 and generally do not have septations Also in the vegetative state they have diploid nuclei whereas fungi have haploid nuclei Most oomycetes produce self motile zoospores with two flagella One flagellum has a whiplash morphology and the other a branched tinsel morphology The tinsel flagellum is unique to the Kingdom Heterokonta Spores of the few fungal groups which retain flagella such as the Chytridiomycetes have only one whiplash flagellum 14 Oomycota and fungi have different metabolic pathways for synthesizing lysine and have a number of enzymes that differ 14 The ultrastructure is also different with oomycota having tubular mitochondrial cristae and fungi having flattened cristae 14 In spite of this many species of oomycetes are still described or listed as types of fungi and may sometimes be referred to as pseudofungi or lower fungi Biology EditReproduction Edit Life cycle of Phytophthora infestans Peronosporales on potato Most of the oomycetes produce two distinct types of spores The main dispersive spores are asexual self motile spores called zoospores which are capable of chemotaxis movement toward or away from a chemical signal such as those released by potential food sources in surface water including precipitation on plant surfaces A few oomycetes produce aerial asexual spores that are distributed by wind They also produce sexual spores called oospores that are translucent double walled spherical structures used to survive adverse environmental conditions Ecology and pathogenicity Edit Unidentified water mold on dead larval mayfly A culture of Achlya sp Saprolegniales isolated from a stream Sea trout suffering from UDN with secondary Saprolegnia infections Many oomycetes species are economically important aggressive algae and plant pathogens 15 16 Some species can cause disease in fish and at least one is a pathogen of mammals The majority of the plant pathogenic species can be classified into four groups although more exist The Phytophthora group is a paraphyletic genus that causes diseases such as dieback late blight in potatoes the cause of the Great Famine of the 1840s that ravaged Ireland and other parts of Europe 17 sudden oak death rhododendron root rot and ink disease in the European chestnut 18 The paraphyletic Pythium group is more prevalent than Phytophthora and individual species have larger host ranges although usually causing less damage Pythium damping off is a very common problem in greenhouses where the organism kills newly emerged seedlings Mycoparasitic members of this group e g P oligandrum parasitize other oomycetes and fungi and have been employed as biocontrol agents One Pythium species Pythium insidiosum also causes Pythiosis in mammals The third group are the downy mildews which are easily identifiable by the appearance of white brownish or olive mildew on the leaf undersides although this group can be confused with the unrelated fungal powdery mildews The fourth group are the white blister rusts Albuginales which cause white blister disease on a variety of flowering plants White blister rusts sporulate beneath the epidermis of their hosts causing spore filled blisters on stems leaves and the inflorescence The Albuginales are currently divided into three genera Albugo parasitic predominantly to Brassicales Pustula parasitic predominantly to Asterales and Wilsoniana predominantly parasitic to Caryophyllales Like the downy mildews the white blister rusts are obligate biotrophs which means that they are unable to survive without the presence of a living host References Edit Arx J A von 1967 Pilzkunde 1 356 Winter G Rabenhorst s Kryptogamen Flora 2nd ed vol 1 part 1 p 32 1880 1879 Dick M W 2001 Straminipilous fungus Dordrecht the Netherlands Kluwer Academic Publishers p 289 oomycete CollinsDictionary com HarperCollins Retrieved 4 June 2014 a b Agrios George 2005 Plant Pathology Elsevier p 409 Vallance J Le Floch G Deniel F Barbier G Levesque C A Rey P 2009 Influence of Pythium oligandrum Biocontrol on Fungal and Oomycete Population Dynamics in the Rhizosphere Applied and Environmental Microbiology 75 14 4790 800 Bibcode 2009ApEnM 75 4790V doi 10 1128 AEM 02643 08 PMC 2708430 PMID 19447961 a b Introduction to the Oomycota Retrieved 2014 07 07 won Bikile3iko el wiktionary org Retrieved 2020 01 22 mykhtas Wiktionary en wiktionary org Retrieved 2020 01 22 Kortekamp A 2005 Growth occurrence and development of septa in Plasmopara viticola and other members of the Peronosporaceae using light and epifluorescence microscopy Mycological Research 109 Pt 5 640 648 doi 10 1017 S0953756205002418 PMID 16018320 a b c Sumbali Geeta Johri B M January 2005 The fungi ISBN 978 1 84265 153 7 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 Silar Philippe 2016 Protistes Eucaryotes Origine Evolution et Biologie des Microbes Eucaryotes HAL Archives ouvertes 1 462 a b c d Van der Auwera G De Baere R Van de Peer Y De Rijk P Van den Broeck I De Wachter R July 1995 The phylogeny of the Hyphochytriomycota as deduced from ribosomal RNA sequences of Hyphochytrium catenoides Mol Biol Evol 12 4 671 8 doi 10 1093 oxfordjournals molbev a040245 PMID 7659021 Agrios George N 2005 Plant Pathology 5th ed Academic Press link Schwelm A Badstober J Bulman S Desoignies N Etemadi M Falloon RE Gachon CM Legreve A Lukes J Merz U Nenarokova A Strittmatter M Sullivan BK Neuhauser S April 2018 Not in your usual Top 10 protists that infect plants and algae Molecular Plant Pathology 19 4 1029 1044 doi 10 1111 mpp 12580 PMC 5772912 PMID 29024322 Haas BJ Kamoun S Zody MC Jiang RH Handsaker RE Cano LM Grabherr M Kodira CD et al 2009 Genome sequence and analysis of the Irish potato famine pathogen Phytophthora infestans Nature 461 7262 393 8 Bibcode 2009Natur 461 393H doi 10 1038 nature08358 PMID 19741609 Vettraino A M Morel O Perlerou C Robin C Diamandis S Vannini A 2005 Occurrence and distribution of Phytophthora species in European chestnut stands and their association with Ink Disease and crown decline European Journal of Plant Pathology 111 2 169 180 doi 10 1007 s10658 004 1882 0 S2CID 2041934 External links EditDescription of The Phylum Oomycota Systematic Biology Introduction to the Oomycota University of California Museum of Paleontology UCMP Genome sequence and analysis of the Irish potato famine pathogen Phytophthora infestans Retrieved from https en wikipedia org w index php title Oomycete amp oldid 1117377190, wikipedia, wiki, book, books, library,
