“the mighty mushroom” take a walk through a forest mushrooms are truly are the largest organisms...
TRANSCRIPT
“The Mighty Mushroom”
• take a walk through a forest • mushrooms are truly are the largest
organisms in the forest• Kingdom Fungi:
– not just mushrooms!– approximately 100,000 species now described– may be as many as 1.5 million species– range from unicellular to complex multicellular
organisms– just about every terrestrial and aquatic
environment– essential decomposers in ecosystems
• critical for the release of nutrients into the ecosystem
– included with animals and plants in the Clade Opisthokonta• diverged about a billion years ago
Nutrition
• like animals, fungi are heterotrophs– cannot make their own food like algae and plants– must go and find it
• unlike animals – they do not ingest their food (i.e. eat)
• fungi decompose & absorb nutrients from its environment
• digestion of both living and dead sources
Body StructureReproductive structure
Hyphae
Spore-producingstructures
Mycelium
20 µm
• most common body structures of a fungus are:– 1. multicellular filaments =
mycelium– 2. yeasts
• mycelium made up of multicellular filaments called hyphae (hypha – singular)
The Mycelium• mycelium body structure:
– the mycelium is a haploid (n) multi-cellular organism
– hyphae enhances the ability to absorb nutrients
– a mycelium infiltrates the material on which it feeds
– the emphasis is on increasing mycelium length NOT width
Reproduction• fungus reproduce asexually & sexually through the production of spores• spores are haploid• spores are carried by wind or water• germination upon exposure to moisture to produce a new mycelium
Haploid (n)
Key
Heterokaryotic(unfused nuclei fromdifferent parents)Diploid (2n)
PLASMOGAMY(fusion of cytoplasm)
Heterokaryoticstage
KARYOGAMY(fusion of nuclei)
Mycelium
SEXUALREPRODUCTION
Zygote
Spores
GERMINATIONMEIOSIS
Spore-producingstructures
ASEXUALREPRODUCTION
Spores
GERMINATION
Spore-producingstructures
• definitions:– karyogamy: fusion of two
haploid nuclei in fungi• production of a diploid
zygote– plasmogamy: fusion of the
cytoplasm NOT the nuclei– plasmogamy produces a
heterokaryotic stage – means different nuclei
• fungal asexual reproduction: through the production of haploid spores by mitosis– the mycelium is haploid and so are the spores = MITOSIS– single-celled yeasts don’t produce a mycelium or spores but simply divide by mitosis or form
progeny by budding
Asexual Reproduction
Haploid (n)
Key
Heterokaryotic(unfused nuclei fromdifferent parents)Diploid (2n)
ASEXUALREPRODUCTION
Spores
GERMINATION
Spore-producingstructures
Mycelium
10 m
Parentcell
Bud
Sexual Reproduction
• fungal sexual reproduction: consists of three stages – plasmogamy karyogamy meiosis– two hyphae of opposite mating type meet and fuse– two cytoplasms fuse = plasmogamy– the two nuclei do not fuse right away – hypha is now called a heterokaryon (different nuclei)
Haploid (n)
Key
Heterokaryotic(unfused nuclei fromdifferent parents)
Diploid (2n)
PLASMOGAMY(fusion of cytoplasm)
Heterokaryoticstage
KARYOGAMY(fusion of nuclei)
Mycelium
SEXUALREPRODUCTION
Zygote
Spores
GERMINATION
MEIOSIS
Spore-producingstructures
ASEXUALREPRODUCTION
Spores
GERMINATION
Spore-producingstructures
Sexual Reproduction
The mycelium is a HAPLOIDmulti-cellular organism
Haploid (n)
Key
Heterokaryotic(unfused nuclei fromdifferent parents)
Diploid (2n)
PLASMOGAMY(fusion of cytoplasm)
Heterokaryoticstage
KARYOGAMY(fusion of nuclei)
Mycelium
SEXUALREPRODUCTION
Zygote(2n)
Spores (n)
GERMINATION
MEIOSIS
Spore-producingstructures
ASEXUALREPRODUCTION
Spores
GERMINATION
Spore-producingstructures
• sexual reproduction: – hours or decades later (!) the nuclei will fuse inside the hypha = karyogamy– production of a diploid zygote (2n)– zygote develops into a spore producing structure called a sporangium– MEIOSIS takes place in the sporangium - producing haploid spores (n)– spores are dispersed to germinate and form a new mycelium
Fungal Diversity
ChytridsZygotefungi
Arbuscularmycorrhizal
fungi
Sacfungi
Clubfungi
• fungi are thought to be descended from a unicelluar, aquatic flagellated protist
• then moved to land – fossils of the earliest vascular land plants
have fungal associations (mycorrhizea)• radiated into 5 Phyla:
– 1. Chytridiomycota– 2. Zygomycota– 3. Glomeromycota– 4. Ascomycota– 5. Basidiomycota
Molds• 1,100 known species in Phylum Zygomycota• diverse in lifestyles• fast-growing molds• e.g. Rhizopus stolonifer – black bread mold
– typical of a zygomycete– mycelium forms as a spread of horizontal hyphae over the food – penetrates it and absorb the
nutrients– spore dispersal through the air eventually passes it onto other substrates for continued growth
Rhizopusgrowingon bread
Matingtype (+) Mating
type (–)
PLASMOGAMY
KeyHaploid (n)Heterokaryotic (n + n)Diploid (2n)
100 µmYoungzygosporangiumSEXUAL
REPRODUCTION
KARYOGAMYZygosporangium
Diploidnuclei
MEIOSISSporangium
Mycelium
Dispersal andgermination
Dispersal andgermination
ASEXUALREPRODUCTION
Sporangia
50 µm
– sexual reproduction: “parents” are mycelia with hyphae or two mating types: “-” and “+”• fusion of two “parental” mycelia with “+” and “-” hyphae• plasmogamy produces a unique structure called a zygosporangium
– heterokaryotic – no nuclear fusion yet!!– zygosporangium can remain dormant for months
Rhizopusgrowingon bread
Matingtype (+) Mating
type (–)
PLASMOGAMY
KeyHaploid (n)Heterokaryotic (n + n)Diploid (2n)
100 µmYoungzygosporangiumSEXUAL
REPRODUCTION
KARYOGAMYZygosporangium(heterokaryotic)
Diploidnuclei
MEIOSISSporangium
Mycelium
Dispersal andgermination
Dispersal andgermination
ASEXUALREPRODUCTION
Sporangia
50 µm
– sexual reproduction:• under favorable conditions – the nuclei in the zygosporangium fuse to make
diploid (2n) nuclei (karyogamy)• zygosporangium starts to make haploid spores (n) via Meiosis• these spores are contained in and released by a sporangium that “sprout” from
the zygosporangium– this is what you see as the fluffy black stuff in black mold
• spores are released to land and germinate into new mycelia on a new substrate
Mushrooms
• club fungus – Phylum Basidiomycota
• 30,000 species• includes the mushrooms, shelf
fungi, molds and mycorrizhae, rusts and smuts
• important decomposers of wood• saprophoric (decomposing) and
parasitic species (rusts and smuts)Fly agaric (Amanita muscoria), a common species in conifer forests in the northern hemisphere
Maiden veil fungus (Dictyphora), a fungus with an odor like rotting meat
Shelf fungi, important decomposers of wood
Puffballs emitting spores
The Common Mushroom
pileus
stipe
stipe
gills
basidiocarp
• basidium = “little pedestal”– spore forming part of the
mushroom• the part of the mushroom we
see is a reproductive structure called a basidiocarp
• basidiocarp = cap (pileus) with the gills on the underside + the supporting stalk = stipe
• the basidiocarp is actually a large aggregation of hyphae forming the mushroom
• underground is the actual mycelium
• sexual reproduction: • two haploid mating types ‘+’ and ‘–’ undergo plasmogamy and a heterokaryotic
mycelium made of two different nuclei per cell forms • rain or temperature changes induce the mycelium to form many basidiocarps
(mushroom) that poke up above the ground
PLASMOGAMY
Key
Haploid (n)Dikaryotic (n + n)Diploid (2n)
SEXUALREPRODUCTION
KARYOGAMY
MEIOSIS
Mycelium
Basidium containingfour haploid nuclei
Dispersal andgermination
Basidium
1 µm
Matingtype (+)
Matingtype (–)
Haploidmycelia
Gills linedwithbasidia
Basidiocarp
Basidia(dikaryotic)
Diploidnuclei
Basidiospore
Basidiospores
• sexual reproduction cont…..: • the gills of the basidiocarp are lined with spore-producing structures (i.e. sporangia) called
basidia (basidium = singular)• within each basidium the 2 nuclei fuse to make a diploid parental cell (i.e. karyogamy)• the parental cell undergoes meiosis 4 haploid nuclei total per basidium• each haploid nuclei develops into a basidiospore (4 basidiospores per basidium)• basidiospores are released and are carried by the wind – germinate into new mycelia which
rapidly undergo more sexual reproduction
4 basidiospores on a basidium
PLASMOGAMY
Key
Haploid (n)Dikaryotic (n + n)Diploid (2n)
SEXUALREPRODUCTION
KARYOGAMY
MEIOSIS
Dikaryoticmycelium
Basidium containingfour haploid nuclei
Dispersal andgermination
Basidium
1 µm
Matingtype (+)
Matingtype (–)
Haploidmycelia
Gills linedwithbasidia Basidiocarp
(dikaryotic)
Basidia
Diploidnuclei
Basidiospore
Basidiospores
Yeasts
• 1500 species of unicellular fungi– not a single taxonomic or phylogenic grouping– divided up between Phylum Ascomycota & Phylum
Basidiomycota• often a synonym for the species Saccharomyces
cerevisiae– but there are several species of yeasts
Yeasts
• are chemotrophs – convert carbohydrates into CO2 and alcohol (fermentation)– yeasts are either obligate aerobes (for cellular
respiration) or anaerobic (fermentation)• naturally occurring on skins of fruits & berries –
even on the skin or epithelial linings of humans– Candida albicans - yeast infections or athlete’s foot
• also found in guts of mammal and insects– e.g. bees and ants
• even in deep sea environments• most reproduce asexually through budding or
fission (mitosis)
Fungal Associations: Lichens
• Lichens: 25,000 species– fungus + green algae (or cyanobacteria)– algae provide organic compounds, the
cyanobacteria fix nitrogen – algae nestle among the fungal hyphae and are
protected
• types of lichens:– 1. Crustose lichens – grow as a crust on a
surface– 2. Foliose lichens – leafy in appearance– 3. Fructicose lichens – shrublike with
branching and intertwined fibrous parts
A fruticose (shrub-like) lichen
A foliose (leaf-like) lichen Crustose (crust-like) lichens
Fungal hyphae
Algal cell
Soredia
Algallayer
Fungalhyphae
Ascocarp of fungus
10 µ
m
Lichens• most reproduce asexually:
– either through fragmentation – or by the formation of soredia – small clusters
of hyphae with embedded algae - may be carried by the wind to new locations