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Zoosporic fungi: Chytridiomycota Kingdom Fungi

Zoosporic fungi: Chytridiomycota Kingdom Fungi. Chytridiomycota & Zygomycota sometimes referred to as “lower fungi” formerly classified in the Phycomycetes = algal fungi thought to have evolved from algae via the loss of chloroplast; no longer excepted theory

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Zoosporic fungi: Chytridiomycota Kingdom Fungi

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  1. Zoosporic fungi: ChytridiomycotaKingdom Fungi

  2. Chytridiomycota & Zygomycota • sometimes referred to as “lower fungi” • formerly classified in the Phycomycetes = algal fungi • thought to have evolved from algae via the loss of • chloroplast; no longer excepted theory • Chytridiomycota and the rest of Kingdom Fungi are • more closely related to animals via protozoan • ancestor (e.g., choanoflagellates)

  3. A SCOMYCOTA C ROWN F UNGI B ASIDIOMYCOTA G LOMALES(ZYGOMYCOTA) KINGDOM F UNGI ZYGOMYCOTA (M UCORALES , E NTOMOPHTHORALES , T RICHOMYCETES ) B LASTOCLADIALES ) (CHYTRIDIOMYCOTA M ONOBLEPHARIDALES ( CHYTRIDIOMYCOTA ) C HYTRIDIALES , N EOCALLIMASTIGALES , S PIZELLOMYCETALES ( CHYTRIDIOMYCOTA ) M ICROSPORIDIA ? O UTGROUPS (C HOANOFLAGELLATES, METAZOA)

  4. Chytridiomycota • General characteristics • only flagellated members of the Kingdom Fungi • chitin cell walls • flattened mitochondrial cristae • AAA lysine biosynthesis • ergosterol • glycogen

  5. Ecology • aquatic & terrestrial • most species are saprobes • some parasites of protists, invertebrates, fungi & plants • some anaerobic species in the rumen of herbivores • recently discovered pathogen of amphibians www.fdrproject.org/pages/disease.htm Batrachochytrium dendrobatidis

  6. Thallus and life history diversity • holocarpic - entire thallus converted into a sporangium • eucarpic - portions of thallus converted into sporangia; • development of vegetative thallus

  7. unicellular - may produce rhizoids that mainly • serve to anchor thallus; rhizoids lack nuclei • filamentous - coenocytic mycelium; septa may form • at base of reproductive structures

  8. endobiotic - living entirely within the cells of their hosts • epibiotic - producing sporangia on the surface of either • a living host or dead organic

  9. Flagellated stages of life cycle • zoospores - asexual reproduction • planogametes - sexual reproduction (not all species) • both zoospores & planogametes possess a single, • posterior whiplash flagellum

  10. Asexual reproduction • initiates with zoosporangium filled with protoplasm • and many nuclei • protoplasm of zoosporangium is incorporated into • numerous zoospores; may involve vesicle formation • zoospores are released, swim, encyst, then germinate • to produce a thallus

  11. operculate zoosporangia form a well-defined circular cap, • operculum, through which the zoospores emerge • inoperculate zoosporangia discharge zoospores through • a discharge tube, formed when papilla dissolves • most known species possess inoperculate zoosporangia

  12. Sexual reproduction • Modes of sexual reproduction • Planogametic copulation (three forms) • isogamous • anisogamous • nonmotile egg fert. by a motile antherozoid • Gametangial copulation • tranfer of protoplast from one gametangium to another • Somatogamy • fusion between rhizoidal filaments

  13. Life cycles • haplobiontic - one free living thallus; • haploid (haplobiontic-haploid) • diploid (haplobiontic-diploid) • diplobiontic - alternation of generation; haploid thallus • alternates with a diploid thallus • Chytridiomycota - examples of both • haplobiontic-haploid (e.g., Chytridium); zygotic meiosis • diplobiontic (e.g., Allomyces); sporangial meiosis

  14. Zoospores • cornerstone of ordinal classification • five zoospore types • basis for ordinal groupings • single whiplash flagellum, rarely polyflagellate cells • attached and directed posteriorly

  15. Zoospores (cont.) • organelles • mitochondria, microbodies, endoplasmic reticulum, and • one to many lipid bodies located in specific regions • some possess microbody-lipid globule complex (MLC) • gamma particle • unique to chytrid zoospores • small membrane-bound organelle containing an • electron-opaque, cup-shaped inclusion • protein storage (?)

  16. Flagellar apparatus • flagellum • kinetosome • (=basal body, flagellated centriole) • dormant kinetosome • (nonfunctional centriole or nfc) • flagellar roots

  17. Microbody-lipid globule complex • (MLC) • assemblage of organelles • lipid bodies in association with • microbodies • mitochondria • membrane cisternae • or rumposomes • not all chytrids have well • organized MLC • functions in utilization of stored • lipid and regulation of calcium

  18. Orders of Chytridiomycota Chytridiales Spizellomycetales Blastocladiales Monoblepharidales Neocallimastigales

  19. Chytridiales true mycelium lacking rhizoids or rhizomycelium present in some species Blyttiomyces Chytridium

  20. Spizellomycetales mainly isolated from soil some are parasites of other fungi and algae Piromyces

  21. Blastocladiales most advanced group (?) mycelial, highly organized zoospores, male and female gametangia, diplobiontic Allomyces

  22. Monoblepharidales oogamous & anisogamous reproduction Foamy mycelium Monoblepharella

  23. Neocallimastigales advanced group obligate anaerobes in rumen & hindgut of herbivores zoospores uni- to polyflagellated Neocallimastix

  24. Life Cycles to Review Blastocladiales (pages 109) Allomyces macrogynus alternate generations, anisogamy Monoblepharidales (page 119) Monoblepharis polymorpha nonmotile egg Chytridiales (page 105) Chytriomyces hyalinus rhizoidal somatangy; operculate Rhizophidium couchii gametangial; inoperculate

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