Fungi (30)

Choanoflagellates/animals/opisthokonts

•Absorptive heterotrophy

•Chitin in cell walls

Fungi's method of obtaining nutrients

Secrete digestive extracellular enzymes that digest food outside the body, then smaller molecules are moved across cell walls

carbon and nutrients directly from dead organic matter.

Absorb nutrients from living hosts

Both partners benefit

• secrete sticky substances so that passing organisms stick tightly to them and hyphae then quickly invade the prey.

some soil fungi make a constricting ring that can trap nematodes

Minute threads in multicellular fungi, form an interwoven mat called mycelium

cells of hyphae are separated by incomplete cross walls or septa with pores that permit organelles to move between cells.

lack septa – multiple nuclei are located within one cytoplasmic mass.

haustoria are nutrient absorbing hyphal tips that press into host cells without breaking through the plasma membranes

Major decomposers on Earth

§Without fungal decomposers, Earth’s carbon cycle would fail; carbon would be buried.

§Saprobic fungi return C to the atmosphere as respiratory CO2, available for photosynthesis by plants.

§Contribute to soil formation and recycling nutrient elements

Mutualistic relationship between fungi and photosynthetic organism

Fungi+plant roots

• 1) Fungi wrap around root
• 2) Fungi penetrate cell walls of root but not plasma membrane

•Production of haploid spore within sporangia.

•Production of naked spores at tips of hyphae called conidia.

•Cell division by unicellular fungi- fission (equal division) or budding (unequal).

•Breakage of the mycelium.

When hyphae of differing mating types fuse but not nuclei

•2 genetically different haploid nuclei coexist within same hyphae.

-Hyphae is neither haploid or diploid, rather it is dikaryotic (n+n)

Fusion of the nuclei

Chytrids and Zygospore

Chytrids, Zygospores, Basiomycota, Ascomycota, Microsporidia, Glomeromycota

Monophyletic group of Basiomycota and Ascomycota

•unicellular fungi, obligate intracellular parasites of animals; 1,500 species.

•They are among the smallest eukaryotes known.

• •The host cell is penetrated by a polar tube of the microsporidian spore, and the contents of the
• spore are injected into the host.

• •The sporoplasm replicates in the host cell and
• produces new infective spores.

•The life cycle of some species is complex and involves multiple hosts.

• •Microsporidia have cell walls with chitin, and
• lack true mitochondria; they have reduced structures called mitosomes.

•DNA sequencing indicates they are highly reduced, parasitic fungi, but exact placement is still debated.

aquatic fungi, were once classed as protists but have chitin in their cell walls.

•Have flagellated gametes, some show alternation of generations (like plants), no dikaryon phase

•Multicellular diploid stage includes a structure that can withstand freezing and drying.

•Chytrids may be parasitic or saprobic; some are found in foregut-fermenting animals such as cattle and deer.

•Some chytrids are unicellular, others have rhizoids, still others are coenocytic.

Infectuous disease killing amphibians throughout the world, killed ~30%, no effective measure for controlling the disease

•conjugating fungi”

•Terrestrial fungi- saprobes on soils, parasites of insects and spiders, as mutualists with other fungi and invertebrates.

•Zygote is the only diploid cell

•Hyphae are coenocytic (lack septa)

•Stalked sporangiophores contain sporangia

•>1000 species described; includes Rhizopus stolonifer, black bread mold.

• Arbuscular mycorrhizae fungi
• Coenocytic hyphae
• Reproduce asexually

• Sac fungi
• produce asci: sacs which contain sexually produced haploid ascospores

Filamentous sac fungi reproduce asexually by conidia that form at the tips of hyphae

Sexual reproduction includes a brief dikaryon

1) Euascomycetes “true”: asci in a fruiting body called an ascocarp.

-“Cup fungi,” includes morels and truffles

-Molds, including Aspergillus and Penicillium

-Ergot—parasite on rye

-Mildews

-Parasites on plants such as chestnut blight and Dutch elm disease

2) Hemiascomycetes “half”: no ascocarp

-Most are unicellular—yeasts

-Baker’s/Brewer’s yeast Saccharomyces cerevisiae

the “club fungi”

•Fruiting structures are basidiomata

•30,000 species, includes edible mushrooms, puff balls, bracket fungi

•Hyphae have septa with pores.

•The basidia are the characteristic sexual reproductive structures; site of nuclear fusion.

• •In mushrooms, basidia form on specialized structures
• called gills or pores.

• •The dikaryon stage may persist for years—some
• live decades or even centuries.

•Also include plant pathogens such as rusts and smuts infect cereal grains. Other club fungi species are fungal partners in ectomycorrhizae.

• Microsporidia = unicellular fungi, 1500 spp.
• •obligate intracellular parasites of animals
• •They are among the smallest eukaryotes known.

• Chytridiomycota = Chytrids, ~1000 spp.
• §Motile zoospores with flagella.
• §Mostly aquatic, once considered protists

• Zygomycota =Zygote fungi, >1000 spp.
• §Resistant zygosporangium as sexual stage.
• §mostly live in soil

• Glomeromycota = arbuscular mycorrhizal (AM) fungi, <200 spp.
• •Reproduce asexually.
• •Associate with plant roots.
• •Live on roots in soil

• Ascomycota= Sac fungi, ~64,000 spp.
• •Sexual spores borne internally in sacs called asci.
• •includes truffles, morels, lichens, some yeasts; some are pathogenic

• Basidiomycota = Club fungi, ~30,000 spp.
• •Sexual spores borne externally on club-shaped structures called basidia.
• •includes mushrooms, rusts, shelf fungi, puffballs, lichens, some yeasts

a rapidly growing, asexually reproducing fungus. Molds are used in the production of antibiotics and cheese. Many molds are classified as “imperfect fungi” because on asexual reproduction is known.

Unicellular members of the zygomycetes, ascomycetes, and basidiomycetes.The term does not refer to a single taxonomic group but rather to a lifestyle that has evolved multiple times.

Found in both Ascomycetes and Basidiomycetes. About 15,000 lichen “species” have been described.