Lecture 17: Fungus Flashcards
how do fungi fit onto the Eukaryotic tree?
more closely related to animals than plants
-it’s its own monophyletic clade
unifying fungal traits
- a number of cell types or unicellular
- heterotrophs that absorb nutrients
- cell wall with chitin
- some have dikaryon stages
- both sexual and asexual reproduction
- three styles of nutrient acquisition
chitin
-polysaccharide that stiffens their cell walls (& gives them structure)
cell types in fungi
-unicellular; can be flagellated (i.e. yeast) or multicellular (filamentous)
hyphae on the fungal body
-long chains of cell-like structures that are joined
septa on the fungal body
- divides cells
- not a complete barrier bc they have pores
- allows for free flow of cytoplasm
- fungi w/ septa are called septate fungi
coenocytic fungi
- don’t have septa
- indicates that cell separation isn’t that important in fungus
mycelium on the fungal body
-groups of hyphae bundled together
fungal digestion/absorptive heterotrophy
- secretes digestive enzymes around them
- enzymes digest what they land on–> absorb organic materials
- external digestion
- nutrients must be in water
how does the fungal body plan reflect nutrient intake in fungus?
-no really defined cells so nutrients can travel faster, therefore fungi grow FAST
cell walls in fungi
-have chitin (not cellulose) (same material as insect exoskeleton) and gives them their structure
fungal nuclei and dikaryons
- dikaryons form from the fusion of 2 haploid mating strains
- rarely differentiation between male and female, instead have mating types (members of same one can’t mate together, lead to greater genetic variation)
dikaryon formation
- fuse
- haploids exist independent but both are transcribed which protects them from bad mutations that happen to haploids (like in mosses)
Asexual and sexual reproduction can occur in one life cycle
-asexual makes more spores, while sexual goes through plasmogamy, fertilization, karyogamy, and makes spores
how are pores reproductive structures?
-by wind they turn into new individuals; produce new spores by mitosis
plasmogamy
- cell fusion
- fusion of cytoplasm
karyogamy
- fertilization
- fusion of nuclei
importance of sexual stages for identification
- sexual stages are used to identify fungus
- making it hard to finalize the fungal phylogeny
microsporidia
- tiny, obligate, intracellular parasites
- infect with a polar tube and then replicated by host cell
- cause things like weight loss
- lack true mitochondria
mitosome
- has double membrane
- looks like mitochondria
- derived from mitochondria, indicates they were lost.
- after this the microsporidia branched off
chytridiomycetes
- likely paraphyletic
- aquatic, unicellular life stages
- flagella present, coenocytic
- can be found in the stomachs of cattle
amphibian decline
- chytrids may be cause bc they kill amphibians that they reside on by producing harmful spores (deadlier at colder temps)
- types: batrachochytrium dendrobatidis (kills amphibians)
zygomycetes
- saprobic or parasitic
- terrestrial, no septa, coenocytic
- sexual reproduction is rare, but still produce zygotes
- gametangia, zygosporangium, and zygospore are found in ONLY this life cycle
gametangia
- are mycorrhizal
- coenocytic
- don’t form mycelia (remain single strands)
- can’t live without host
- all terrestrial
zygosporangium
- gametes mate in it
- leads to many unfused nuclei
- once they fuse, you get a multinucleate
zygospore
- multinucleate
- all nuclei inside are 2n
- can remain dormant and eventually portions of it will undergo meiosis and produce spores
glomeromycetes
- only 150 species and made invasion of land by plants possible
- coenocytic
- don’t form mycelia
mycorrhizae
- form mutualistic relationships with plants
- hyphae grow in roots of trees and plants
- allows for beneficial nutrients exchange for both
- they can’t live without their hosts b/c get their sugars from the host’s photosynthesis
- monophyletic
ascomycetes
- septate
- dikaryon forming but short dikaryon phase and then becomes diploid
- bear spores in cups
- types: cup fungus, yeast, penicillin, truffle/morels, cheese molds, chestnut blight, dutch elm disease.
basidiomycetes
- most well known, contains most mushrooms
- basidiocarps (puffball reproductive structures)
- septate and dikaryon forming
- dikaryon stage can persist for years
mutualists
- exchange nutrients with other species
- live in conjunction with other species
saprophytes
- digest/eat dead materials
- “decomposers”
parasites
- eat living tissue on living organisms
- types: athlete’s foot, ringworm
why are fungal diseases so hard to treat?
- bc they typically attack other eukaryotes
- its hard to treat the fungus without “treating” the host.
