Chytridiomycota

Abstract

The Chytridiomycota is a phylum in the kingdom Fungi, whose members produce unwalled, asexual spores that swim by means of a single, posteriorly directed flagellum. Members are microscopic saprobes or parasites found in fresh and saline water and soils. The phylum contains two classes, the Monoblepharidomycetes with one order and the Chytridiomycetes with seven orders and several undescribed groups. Orders are based on molecular and ultrastructural characters. Many species of chytrids were described without these characters and need to be re‚Äźexamined to place them in the proper orders and genera. Chytrids are important as degraders of cellulose, keratin and chitin and also as algal pathogens, sometimes controlling algal blooms. A few are plant pathogens with Synchytrium endobioticum causing black wart of potatoes. The rhizophydialean chytrid Batrachochytrium dendrobatidis grows in keratinised skin cells of amphibians and is pathogenic to many species, causing amphibian population declines on several continents and extirpation of some species.

Key Concepts:

  • Members of the Chytridiomycota are ubiquitous in aquatic and terrestrial habitats and can be found by microscopically examining baits placed with aquatic debris or with soil plus water.

  • Chytridiomycota reproduce primarily by zoospores, which are mitotically produced, contained by a membrane and motile via a posteriorly directed flagellum.

  • Because of convergent evolution of light microscopic characters, many genera described before the molecular era are polyphyletic and may not be placed in the correct order.

  • Systematics in the Chytridiomycota relies on transmission electron microscopic features of zoospores and on DNA sequence information.

  • Algal parasites are usually species specific and are capable of affecting population levels of planktonic algae.

  • Batrachochytrium dendrobatidis is a chytrid pathogen of amphibians responsible for some amphibian population declines on at least five continents.

Keywords: chytrid; chytridiomycetes; aquatic fungi; fungus; zoosporic fungi

Figure 1.

Major types of development in the Chytridiomycota: (a) endogenous; (b) exogenous, monocentric; (c) exogenous‐endogenous; (d‐f) polycentric; (d) rhizomycelial; (e) mycelial; (f) colonial. ant, antherozoid; o, operculum; oog, oogonium; rs, resting spore; zc, zoospore cyst; zsp, zoosporangium.

Figure 2.

Current phylogenetic theory of Chytridiomycota (orders and clades), Neocallimastigomycota, and Blastocladiomycota, constructed from ribosomal DNA operon sequences (adapted from James et al., ). Authors and year of description or emendment for phyla and orders in parentheses.

Figure 3.

Schematic representation of the kinetosomal areas of the eight orders in the Chytridiomycota: (a) Monoblepharidales; (b) Chytridiales; (c) Cladochytriales; (d) Lobulomycetales; (e) Polychytriales; (f) Rhizophydiales; (g) Rhizophlyctidales; (h) Spizellomycetales. G, Golgi apparatus; K, kinetosome; mb, microbody; mt, microtubule root; MTOC, microtubule organising center; N, nucleus; NFC, nonflagellated centriole; pl, plates; Rh, rhizoplast; SI, striated inclusion.

Figure 4.

Thalli of Batrachochytrium dendrobatidis in skin cells of a northern leopard frog (Lithobates pipiens).

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References

Abeliovich A and Dikbuck S (1977) Factors affecting infection of Scenedesmus obliquus by a Chytridium sp. in sewage oxidation ponds. Applied and Environmental Microbiology 34: 832–836.

Annis SL, Dastoor FP, Ziel H, Daszak P and Longcore JE (2004) A DNA‐based assay identifies Batrachochytrium dendrobatidis in amphibians. Journal of Wildlife Diseases 40: 420–428.

Barr D and DéSaulniers NL (1986) Four zoospore subtypes in the Rhizophlyctis‐Karlingia complex (Chytridiomycetes). Canadian Journal of Botany 64: 561–572.

Barr DJS (1980) An outline for the reclassification of the Chytridiales and for a new order, the Spizellomycetales. Canadian Journal of Botany 58: 2380–2394.

Barr DJS (1987) Isolation, culture and identification of Chytridiales, Spizellomycetales, and Hyphochytriales. In: Fuller MS and Jaworski A (eds) Zoosporic Fungi in Teaching & Research, pp. 118–120. Athens, Georgia: Southeastern Publishing Corporation.

Barr DJS (2000) Chytridiomycota. In: McLaughlin DJ, McLaughlin EG and Lemke PA (eds) The Mycota VII, Systematics and Evolution, pp. 93–112. Berlin: Springer.

Berger L, Speare R, Daszak P et al. (1998) Chytridiomycosis causes amphibian mortality associated with population declines in the rain forests of Australia and Central America. Proceedings of the National Academy of Sciences of the USA 95: 9031–9036.

Boyle DG, Olsen V, Morgan JAT and Hyatt AD (2004) Rapid quantitative detection of chytridiomycosis (Batrachochytrium dendrobatidis) in amphibian samples using real‐time Taqman PCR assay. Diseases of Aquatic organisms 60: 141–148.

Doggett MS and Porter D (1996) Sexual reproduction in the fungal parasite. Zygorhizidium Planktonicum. Mycologia 88: 720–732.

van Donk E (1989) The role of fungal parasites in phytoplankton succession. In: Sommer U (ed.) Plankton Ecology: Succession in Plankton Communities, pp. 171–194. New York: Springer.

Farrer RA, Weinert LA, Bielby J et al. (2011) Multiple emergences of genetically diverse amphibian‐infecting chytrids include a globalized hypervirulent recombinant lineage. Proceedings of the National Academy of Sciences, doi: 10.1073/pnas.1111915108.

Freeman KR, Martin AP, Karki D et al. (2009) Evidence that chytrids dominate fungal communities in high‐elevation soils. Proceedings of the National Academy of Sciences of the USA 106: 18315–18320.

Garner TWJ, Perkins MW, Govindarajulu P et al. (2006) The emerging amphibian pathogen Batrachochytrium dendrobatidis globally infects introduced populations of the North American bullfrog, Rana catesbeiana. Biology Letters 2: 455–459.

Gleason FH, Schmidt SK and Marano AV (2010) Can zoosporic true fungi grow or survive in extreme or stressful environments? Extremophiles 14: 417–425.

Hibbett DS, Binder M, Bischoff JF et al. (2007) A higher‐level phylogenetic classification of the Fungi. Mycological Research 111: 509–547.

Holfeld H (2000) Relative abundance, rate of increase, and fungal infections of freshwater phytoplankton. Journal of Plankton Research 22: 987–995.

Ibelings BW, Gsell AS, Mooij WM et al. (2011) Chytrid infections and diatom spring blooms: paradoxical effects of climate warming on fungal epidemics in lakes. Freshwater Biology 56: 754–766.

James TY, Kauff F, Schoch CL et al. (2006a) Reconstructing the early evolution of fungi using a six‐gene phylogeny. Nature 443: 818–822.

James TY, Letcher PM, Longcore JE et al. (2006b) A molecular phylogeny of the flagellated fungi (Chytridiomycota) and description of a new phylum (Blastocladiomycota ). Mycologia 98: 860–871.

James TY, Litvintseva AP, Vilgalys R et al. (2009) Rapid global expansion of the fungal disease chytridiomycosis into declining and healthy amphibian populations. PLoS Pathogens 5(5): e1000458.

James TY, Porter D, Leander CA, Vilgalys R and Longcore JE (2000) Molecular phylogenetics of the Chytridiomycota supports the utility of ultrastructural data in chytrid systematics. Canadian Journal of Botany 78: 336–350.

Joneson S, Stajich JE, Shiu SH and Rosenblum EB (2011) Genomic transition to pathogenicity in chytrid fungi. PLoS Pathogens 7(11): e1002338.

Kagami M, Bruin A de, Ibelings BW and Donk EV (2007) Parasitic chytrids: their effects on phytoplankton communities and food‐web dynamics. Hydrobiologia 578: 113–129.

Kagami M, Helmsing NR and Donk E (2010) Parasitic chytrids could promote copepod survival by mediating material transfer from inedible diatoms. Hydrobiologia 659: 49–54, doi: 10.1007/s10750‐010‐0274‐z.

Küpper FC, Maier I, Müller DG, Loiseaux‐de Goer S and Guillou L (2006) Phylogenetic affinities of two eukaryotic pathogens of marine macroalgae, Eurychasma dicksonii (Wright) Magnus and Chytridium polysiphoniae Cohn. Cryptogamie Algologie 27: 165–184.

Le Calvez T, Burgaud G, Mahé S, Barbier G and Vandenkoornhuyse P (2009) Fungal diversity in deep‐sea hydrothermal ecosystems. Applied and Environmental Microbiology 75: 6415–6421.

Letcher PM, Powell MJ, Barr DJS et al. (2008) Rhizophlyctidales – a new order in Chytridiomycota. Mycological Research 112: 1031–1048.

Letcher PM, Powell MJ, Churchill PF and Chambers JG (2006) Ultrastructural and molecular phylogenetic delineation of a new order, the Rhizophydiales (Chytridiomycota). Mycological Research 110: 898–915.

Lips KR, Brem FMR, Brenes R et al. (2006) Emerging infectious disease and the loss of biodiversity in a neotropical amphibian community. Proceedings of the National Academy of Sciences 103: 3165–3170.

Longcore JE, Pessier AP and Nichols DK (1999) Batrachochytrium dendrobatidis gen. et. sp. nov., a chytrid pathogenic to amphibians. Mycologia 91: 219–227.

Longcore JE and Simmons DR (2012) The Polychytriales ord. nov. contains chitinophilic members of the rhizophlyctoid alliance. Mycologia, (Published online: September 13, 2011, doi: 10.3852/11‐193).

Lozupone CA and Klein DA (2002) Molecular and cultural assessment of chytrid and Spizellomyces populations in grassland soils. Mycologia 94: 411–420.

Morehouse EA, James TY, Ganley ARD et al. (2003) Multilocus sequence typing suggests the chytrid pathogen of amphibians is a recently emerged clone. Molecular Ecology 12: 395–403.

Mozley‐Standridge SE, Letcher PM, Longcore JE, Porter D and Simmons DR (2009) Cladochytriales – a new order in Chytridiomycota. Mycological Research 113: 498–507.

Nyvall P, Pedersén M and Longcore JE (1999) Thalassochytrium gracilariopsidis (Chytridiomycota), gen et sp. nov, endosymbiotic in Gracilariopsis sp. (Rhodophyceae). Journal of Phycology 35: 176–185.

Powell MJ (1993) Looking at mycology with a Janus face: a glimpse at Chytridiomycetes active in the environment. Mycologia 85: 1–20.

Powell MJ and Roychoudhury S (1992) Ultrastructural organization of Rhizophlyctis harderi zoospores and redefinition of the type 1 microbody–lipid globule complex. Canadian Journal of Botany 70: 750–761.

Schloegel LM, Ferreira CM, James TY et al. (2010) The North American bullfrog as a reservoir for the spread of Batrachochytrium dendrobatidis in Brazil. Animal Conservation 13: 53–61, doi: 10.1111/j.1469‐1795.2009.00307.x.

Simmons DR, James TY, Meyer AF and Longcore JE (2009) Lobulomycetales, a new order in the Chytridiomycota. Mycological Research 113: 450–460.

Simmons DR, Letcher PM, Powell MJ and Longcore JE (2012) Alogomyces tanneri gen. et sp. nov., a chytrid in Lobulomycetales from horse manure. Mycologia, Published online: August 9, 2011, doi: 10.3852/11‐043.

Sønstebø JH and Rohrlack T (2011) Possible implications of chytrid parasitism for population subdivision in freshwater cyanobacteria of the genus Planktothrix. Applied and Environmental Microbiology 77: 1344–1351, doi: 10.1128/AEM.02153‐10.

Sparrow FK (1960) The Phycomycetes, 2nd revised edn Ann Arbor, MI: University of Michigan Press.

Steiger RA, Simmons DR and Longcore JE (2011) Cylindrochytridium hohnstonii Karling is a member of the Cladochytriales. Mycotaxon (in press).

Stoeck T and Epstein S (2003) Novel eukaryotic lineages inferred from small‐subunit rRNA analyses of oxygen‐depleted marine environments. Applied and Environmental Microbiology 69: 2657–2663.

Vélez CG, Letcher PM, Schultz S, Powell MJ and Churchill PF (2011) Molecular phylogenetic and zoospore ultrastructural analyses of Chytridium olla establish the limits of a monophyletic Chytridiales. Mycologia 103: 118–130.

Wager H (1913) Life‐history and cytology of Polyphagus euglenae. Annals of Botany 27: 173–202.

Wakefield WS, Powell MJ, Letcher PM et al. (2010) A molecular phylogenetic evaluation of the Spizellomycetales. Mycologia 102: 596–604.

Weldon C, Preez LH, du Hyatt AD, Muller R and Speare R (2004) Origin of the amphibian chytrid fungus. Emerging Infectious Diseases 10: 2100–2105.

Whisler HC (1987) On the isolation and culture of water molds: the Blastocladiales and Monoblephyaridales. In: Fuller MS and Jaworski A (eds) Zoosporic Fungi in Teaching & Research, pp. 121–124. Athens, Georgia: Southeastern Publishing Corporation.

Further Reading

Barr DJS (1990) Phylum Chytridiomycota. In: Margulis L, Corliss JO, Melkonian M and Chapman DJ (eds) Handbook of Protoctista, pp. 454–466. Boston, MA: Jones and Bartlett.

Canter‐Lund H and Lund JWG (1995) Fungi living on and in algae. In: Canter‐Lund H and Lund JWG (eds) Freshwater Algae, Their Microscopic World Explored, pp. 279–324. Bristol: Biopress.

Fuller MS (1996) The flagellated fungal spore. In: Sutton B (ed.) A Century of Mycology, pp. 161–192. Cambridge: Cambridge University Press.

Fuller MS and Jaworski A (eds) (1987) Zoosporic Fungi in Teaching and Research. Athens, GA: Southeastern Publishing.

Karling JS (1977) Chytridiomycetarum iconographia. Lehre, Germany: J. Cramer.

Longcore JE (1996) Chytridiomycete taxonomy since 1960. Mycotaxon 60: 149–174.

Sparrow FK (1973) Chytridiomycetes, Hyphochytridiomycetes. In: Ainsworth GC, Sparrow FK and Sussman AS (eds) The Fungi, IV B, pp. 85–110. New York: Academic Press.

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How to Cite close
Longcore, Joyce E, and Simmons, D Rabern(May 2012) Chytridiomycota. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0000349.pub3]