Lect. 21 - Fungi

unikont

A eukaryotic cell with no more than one single flagellum; thought to be the ancestor of all animals

opisthokont

Organisms that descended from an ancestor with a posterior flagellum, including fungi, animals, and certain protists

nucleariids

Sister Taxon of fungi, group of unicellular, amoeboid protists

Absorptive Herterotrophs

Absorbs small organic compounds from the external environment and use them for both energy and as a carbon source

chitin

A fibrous polysaccharide that makes up the cell walls of fungi and the exoskeleton of crustaceans and insects. A polymer version of glucose modified to contain some Nitrogen

yeast

unicellular fungi

hyphae

each of the branching filaments that make up the mycelium/body of a fungus

mycelium

densely branched network of the hyphae of a fungus

septate hyphae

hyphae with incomplete cross walls called septae (pores in septae sometimes allow nuclei to move across)

coenocytic hyphae

hyphae that contain no septa and appear as long, continuous cells with many nuclei

fruiting body

reproductive structure of a fungus that grows from the mycelium

spore

haploid spores may be produced sexually (syngamy & meiosis) or asexually (mitosis & budding)

conidia

spores formed asexually in the sporangia or at the tips of the hyphae

plasmogamy

when two haploid fungi (of different mating types) fuse with each other

karyogamy

after fusion and formation of the n+n heterokaryon, the nuclei fuse to form diploid cells

heterokaryon

A mycelium cell formed by the fusion of two hyphae that have genetically different nuclei (n+n)

n+n

The dikaryon produced following plasmogamy of (+) and (-) mating type filaments

haustoria

modified hyphae on many parasitic fungi that penetrate the tissues of their hosts to absorb their nutrients

mycorrizhae

Mutalistic fungi with plant roots: Fungi help with water/mineral absorption; plants supply fungi with carbon

Ectomycorrhizae

A type of mycorrhizae in which the mycelium forms a cover around plant roots, but does NOT penetrate cell walls

arbuscular mycorrhizae

Fungal hyphae penetrate plant roots and enter cell walls (but does not penetrate cell membranes)

endophytic fungi

Mutualistic/commensal fungi that live in the above-ground parts of plants (seen in ALL terrestrial plants. Deter grazers and help plants resist stresses (heat, low water)

lichen

Symbiosis formed by a fungus (usually Ascomycota) and a photosynthetic organism (usually cyanobacteria/green algae). Hyphae provide nutrients, photosynthetic cells provide carbon

photosynthate

a sugar or other carbohydrate made by chemical process of photosynthesis

soredia

clusters of algal cells (photosynthetic cells) and mycelia (fungal cells) that allow lichens to propagate

lichenometry

determine the age of exposed rock surfaces based on the size of lichen (slow growth)

chytrids

A fungal phylum that:

- needs aquatic, damp environment

- some multicellular some unicellular

- consists of decomposers, parasites, and some mutualists

zygomycetes

A fungal phylum that:

- are all terrestrial (damp)

- coenocytic (no septae)

- some decomposers (molds), some parasites/commensals of animals

- high food supply (asexual reproduction) low food supply (sexual)

- formation of a zygosporangium

glomeromycetes

A fungal phylum that:

- arbuscular mycorrhizas with liverworts and the roots of vascular land plants

- coenocytic

dikaryon

A cell carrying two genetically distinguishable nuclei (same as heterokaryon, but ONLY TWO distinct nuclei, rather than two or more)

ascomycetes

A fungal phylum that:

- sister taxa with basidiomycetes

- septate hyphae

- have a dikaryon stage after plasmogamy and before karyogamy

- is called sac fungus (due to saclike structure in which the spores develop)

- marine, freshwater, and terrestrial

- most multicelluar

mating type

fungal haploid + or - mating types (pheromones), will undergo plasmogamy to become dikaryon

zygosporangium

thick-walled sexual structure that characterizes members of the phylum Zygomycota

ascocarp

The fruiting body of a sac fungus (ascomycete)

ascus

saclike structure in which ascospores are formed through sexual reproduction of ascomycetes

ascospore

haploid spore produced within the ascus of ascomycetes

basidiomycetes

A fungal phylum that:

- sister taxa with ascomycetes

- septate hyphae

- have a dikaryon stage after plasmogamy and before karyogamy

-include many mushroom and puffballs

- all multicellular

- "club fungi"

- fruiting body called basidiocarp (produces basidia, where karyogamy occurs)

What is the sister taxon to the fungi? To what major protist clade do the fungi belong to?

- sister taxon: nucleariids (unicellular amoeba)

- protist clade: unikonts/opisthokonts

When did fungi originate?

460 mya

How do fungi acquire energy and carbon?

Absorptive chemoheterotrophs - absorb small organic compounds from environment

Describe the structures of unicellular and multicellular fungi

unicellular (yeasts): whole cell is the ascus

multicellular: made of many tubular filaments "hyphae" that can be septate or coenocytic

Describe the various ways that fungi produce spores

Fungi produce spores either asexually (by mitosis) or sexually (by meiosis)

Asexual spores: sporangiospores, conidia, and budding blastospores

Sexual spores: zygospores, ascospores, and basidiospores formed through fusion/plasmogamy

Fungi are either haploid, diploid, or "n+n" in various parts of their lifecycles. What is this n+n business?

Fungi are "n+n" during the heterokaryon/dikaryon state following plasmogamy, the fusing of two different haploid mating cells

How do fungi mate?

- same mating types do not fuse with each other

- sense each other by pheromones

- hyphae of two mating types grow towards one another. At the place they meet, they form gametangia, and then plasmogamy occurs to make a zygosporangium (n+n)

Why are fungi so important ecologically?

- decomposers of cellulose and lignin (rid of carcasses, soil formation, carbon return)

- form essential mutalistic symbiosis with plants to provide nutrients

What are lichens? How do they reproduce?

- stable symbioses formed by a fungus + a photosynthetic organism

- reproduction: can reproduce by fragmentation or by producing soredia (a few photosynthetic cells bound by fungal hyphae)