1. Lecture #4
Fungi

2. “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

3. Nutrition like animals, fungi are heterotrophs
cannot make their own food like algae and plants
unlike animals – they do not ingest their food
fungi absorb nutrients from its environment
digestion of both living and dead sources

4. Body Structure most common body structures are:
Reproductive structure
Hyphae
Spore-producing
structures
Mycelium
20 µm
most common body structures are:
1. multicellular filaments
2. yeasts
relatively few species grow as yeasts
those that do inhabit moist environments
most grow as multicellular filaments called hyphae (hypha – singular)
cell wall is strengthened by chitin
(not cellulose = plants)
chitin - nitrogen containing polysaccharide
strong yet flexible

5. Body Structure body structure:
hyphae enhances the ability to absorb nutrients
hyphae form an interwoven mass called a mycelium (mycelia plural)
a mycelium infiltrates the material on which it feeds
mycelia grow very fast – nutrients for growth are carried rapidly via cytoplasmic streaming to the growing hyphae
the emphasis is on increasing mycelium length NOT width
Body Structure
Nuclei
Septate hypha
Septum
Pore
Cell wall
Coenocytic hypha
Reproductive structure
Hyphae
Spore-producing
structures
Mycelium
20 µm

6. Fungal Hyphae
septate hyphae are divided into individual cells by walls called septa
septa have relatively large pores to allow for the passage of ribosomes, mitochondria and nuclei between cells
those that lack septa are called ceonocytic fungi
Nuclei
Septate hypha
Septum
Pore
Cell wall
Coenocytic hypha

7. Mycorrhizal Fungus
mycorrhizal fungi: fungi with mutually beneficial relationships between the fungus and plant roots
mycorrhiza = symbiotic relationship between a fungus and the root of a vascular plant
the hyphae are specialized = form haustoria that project into a plant cell
but do not penetrate it
haustoria remain separated from the plant by the plant’s plasma membrane!
very common type - ectomycorrhizal fungi= sheaths of hyphae grow over the root
Fungal hypha
Haustorium
Plant cell
Haustoria
plasma
membrane
Plant
cell
wall

8. Reproduction definitions:
fungus reproduce through the production of spores
spores are carried by wind or water
germination upon exposure to moisture to produce a new mycelium
definitions:
karyogamy: fusion of two haploid nuclei in fungi
production of a diploid zygote
plasmogamy: fusion of the cytoplasm NOT the nuclei
produces a heterokaryotic stage – means different nuclei
Haploid (n)
Key
Heterokaryotic
(unfused nuclei from
different parents)
Diploid (2n)
PLASMOGAMY
(fusion of cytoplasm)
stage
KARYOGAMY
(fusion of nuclei)
Mycelium
SEXUAL
REPRODUCTION
Zygote
Spores
GERMINATION
MEIOSIS
Spore-producing
structures
ASEXUAL

9. Sexual Reproduction
fungal sexual reproduction: consists of three stages – plasmogamy karyogamy  meiosis
two hyphae of different mating type extends towards each other – production of pheromones
the hyphae meet and fuse
two cytoplasms fuse = plasmogamy
nuclei from these two “parental” fungi do not fuse right away – fungus is now called a heterokaryon
Haploid (n)
Key
Heterokaryotic
(unfused nuclei from
different parents)
Diploid (2n)
PLASMOGAMY
(fusion of cytoplasm)
stage
KARYOGAMY
(fusion of nuclei)
Mycelium
SEXUAL
REPRODUCTION
Zygote
Spores
GERMINATION
MEIOSIS
Spore-producing
structures
ASEXUAL

10. Sexual Reproduction sexual reproduction: The mycelium is a HAPLOID
hours or decades later (!) the nuclei will fuse = karyogamy
production of a diploid zygote (2n)
formation of 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
Haploid (n)
Key
Heterokaryotic
(unfused nuclei from
different parents)
Diploid (2n)
PLASMOGAMY
(fusion of cytoplasm)
stage
KARYOGAMY
(fusion of nuclei)
Mycelium
SEXUAL
REPRODUCTION
Zygote
Spores
GERMINATION
MEIOSIS
Spore-producing
structures
ASEXUAL
The mycelium is a HAPLOID
multi-cellular organism

11. fungal asexual reproduction: most fungi can reproduce sexually and asexually depending on nutrient availability
some fungi (molds) reproduce asexually through their mycelium making haploid spores (by mitosis)
other reproduce asexually by binary fission or budding - single-celled yeasts
yeasts don’t produce spores
10 m
Parent
cell
Bud
Haploid (n)
Key
Heterokaryotic
(unfused nuclei from
different parents)
Diploid (2n)
PLASMOGAMY
(fusion of cytoplasm)
stage
KARYOGAMY
(fusion of nuclei)
Mycelium
SEXUAL
REPRODUCTION
Zygote
Spores
GERMINATION
MEIOSIS
Spore-producing
structures
ASEXUAL

12. Fungal Diversity
fungi are thought to be descended from a unicelluar, aquatic flagellated protist
earliest lineages of fungus thought to possess flagella
some still have flagella – called chytrids
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
Chytrids
Zygote
fungi
Arbuscular
mycorrhizal
Sac
Club
Basidiomycota
Ascomycota
Glomeromycota
Zygomycota
Chytridiomycota

13. 1. Phylum: Chytridiomycota
known as the chytrids
most primitive of the fungi - diverged the earliest in fungal evolution
unique in that they have flagellated spores called zoospores
some exist as single cells, others form colonies with hyphae
do not have a true mycelium – fungal body is called a thallus
are considered a coenocytic fungus – no septa in their hyphae
extensions off the hyphae produce digestive enzymes for decomposition of their substrate
Hyphae
1. Phylum: Chytridiomycota

14. 2. Phylum: Zygomycota 1,100 known species 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
hyphae are mainly coenocytic
spore dispersal through the air eventually passes it onto other substrates for continued growth

15. sexual reproduction: “parents” are mycelia with hyphae or two mating types: “-” and “+”
+ and – hypha extend toward one another (pheromones)
two gametangia form between these hyphae – each contains multiple haploid nuclei that are similar to gametes
two gametangia undergo plasmogamy to produce a zygosporangium
said to be heterokaryotic – no nuclear fusion yet!!
zygosporangium thickens and forms a “cyst” – remains resistant and dormant for months
Rhizopus
growing
on bread
Mating
type (+)
type (–)
Gametangia with
haploid nuclei
PLASMOGAMY
Key
Haploid (n)
Heterokaryotic (n + n)
Diploid (2n)
100 µm
Young
zygosporangium
(heterokaryotic)
SEXUAL
REPRODUCTION
KARYOGAMY
Zygosporangium
Diploid
nuclei
MEIOSIS
Sporangium
Mycelium
Dispersal and
germination
ASEXUAL
Sporangia
50 µm

16. sexual reproduction:
under favorable conditions – karyogamy occurs in the zygosporangium => diploid nuclei inside the zygosporangium (parental cells for meiosis)
followed by meiosis into haploid spores
from the cyst arises a sporangium (called a fruiting body) for the production of haploid spores
this is what we see as the black fuzziness on bread
spores germinate into new + and - mycelia
Rhizopus
growing
on bread
Mating
type (+)
type (–)
Gametangia with
haploid nuclei
PLASMOGAMY
Key
Haploid (n)
Heterokaryotic (n + n)
Diploid (2n)
100 µm
Young
zygosporangium
(heterokaryotic)
SEXUAL
REPRODUCTION
KARYOGAMY
Zygosporangium
Diploid
nuclei
MEIOSIS
Sporangium
Mycelium
Dispersal and
germination
ASEXUAL
Sporangia
50 µm

17. 3. Phylum Ascomycota cup fungus 60,000 species
The cup-shaped ascocarps (fruiting bodies) of Aleuria aurantia give this species its common name: orange peel fungus.
The edible ascocarp of Morchella esculenta, the succulent morel is often found under trees in orchards.
10 µm
Tuber melanosporum is a truffle, an ascocarp that grows underground and emits strong odors. These ascocarps have been dug up and the middle one sliced open.
Neurospora crassa feeds as a mold on bread and other food (SEM).
cup fungus
60,000 species
red, blue and green molds
also includes mildews
defined by the formation of a cup-like ascocarp
a sac-like reproductive structure containing asci that produce haploid spores edible portion of this fungus
e.g. morels and truffles
half the species associate with algae to form lichens
most are septate within their hyphae

18. 3. Phylum Ascomycota
mildews: general term of mildew means dicolorations and odors created by fungus
mildews are actually are parasitic fungi of plants
white powdery appearance

19. sexual reproduction:
fusion of the hyphae from opposite mycelia mating types produces a new mycelium where the touching hyphae undergo plasmogamy (just like in the zygomycotes)
this new mycelium is made up of dikaryotic hyphae (2 unfused nuclei inside)
at the tip of each of some of these hyphae a dikaryotic ascus forms (plural = asci)
PLASMOGAMY
Key
Haploid (n)
Dikaryotic (n + n)
Diploid (2n)
SEXUAL
REPRODUCTION
KARYOGAMY
Four
haploid
nuclei
MEIOSIS
Dikaryotic
Hyphae
ASEXUAL
Diploid nucleus
(zygote)
Dispersal
Germination
Mycelium
Mycelia
Conidiophore
Conidia;
mating type (–) or (+)
fusion of (+)
and (-)
hyphae
Ascus
(dikaryotic)
Eight
ascospores
Asci
Ascocarp

20. sexual reproduction:
within each individual ascus – karyogamy unites the 2 nuclei and meiosis follows to form 4 haploid nuclei
each of these 4 nuclei divide by mitosis ONCE to form a total of 8 ascospores each with a single nuclei
multiple asci become surrounded by a protective ascocarp (aggregation of hyphae) – that sprouts above the soil
ascospores are ejected from this ascocarp to germinate and form new mycelia
PLASMOGAMY
Key
Haploid (n)
Dikaryotic (n + n)
Diploid (2n)
SEXUAL
REPRODUCTION
KARYOGAMY
Four
haploid
nuclei
MEIOSIS
Hyphae
extending from
ascogonium
Diploid nucleus
(zygote)
Mycelia
fusion of (+)
and (-)
hyphae
Ascus
(dikaryotic)
Eight
ascospores
Asci
Ascocarp
Germination
Dispersal

21. asexual reproduction: fungus produces a powdery structures called conidiophores at the tip of their hyphae
conidiophore is equivalent to a asexual sporangium
mitosis within the conidiophore produces spores called conidia
conidia carried by air currents to new locations
germination leads to specialized hyphae formation called haustoriae – penetrate the epidermis of leaves and absorb nutrients
eventual production of a new mycelium with new conidiophores
PLASMOGAMY
Key
Haploid (n)
Dikaryotic (n + n)
Diploid (2n)
SEXUAL
REPRODUCTION
KARYOGAMY
Four
haploid
nuclei
MEIOSIS
Dikaryotic hyphae
extended from
ascogonium
ASEXUAL
Diploid nucleus
(zygote)
Dispersal
Germination
Mycelium
Mycelia
Conidiophore
Conidia;
mating type (–)
Mating
type (+)
Ascus
(dikaryotic)
Eight
ascospores
Asci
Ascocarp
e.g. Neurospora crassa conidiophore
( green bread mold)

22. 4. Phylum: Basidiomycota
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
club fungus
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)

23. 4. Phylum: Basidiomycota
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
all are characterized by the formation of a basidium (plural = basidia) – club-shaped structure which is diploid and produces basidiospores
basidia are located on the visible mushroom called the basidiocarp and are the structures we call mushrooms, puffballs, toadstools, bracket fungus
beneath the basidiocarp are extensive mats of mycelia that feed on decaying vegetation – very long lived and dikaryotic
hyphae of the mycelium are septate and coenocytic at specific stages during their reproduction

24. The Common Mushroom the basidiomycotes include the common mushroom
pileus
the basidiomycotes include the common mushroom
basidium = “little pedestal”
note the cap (pileus) with the gills on the underside
the supporting stalk = stipe
fruiting body or basidiocarp = cap + stalk
as in the ascomycotes and its ascocarp – the basidiocarp is an aggregation of hyphae
basidiocarp
stipe
stipe
gills

25. sexual reproduction:
two haploid mating types ‘+’ and ‘–’ undergo plasmogamy and a dikaryotic mycelium forms made up many dikaryotic hyphae
rain or temperature changes induce the dikaryotic mycelium to form a basidiocarp (mushroom)
the hyphae of the mushroom are still dikaryotic – no nuclear fusion yet (nuclei are still separated and are haploid)
PLASMOGAMY
Key
Haploid (n)
Dikaryotic (n + n)
Diploid (2n)
SEXUAL
REPRODUCTION
KARYOGAMY
MEIOSIS
Dikaryotic
mycelium
Basidium containing
four haploid nuclei
Dispersal and
germination
Basidium
1 µm
Mating
type (+)
type (–)
Haploid
mycelia
Gills lined
with
basidia
Basidiocarp
(dikaryotic)
Basidia
Diploid
nuclei
Basidiospore
Basidiospores

26. the gills of the basidiocarp are made of dikaryotic hyphae
sexual reproduction:
the gills of the basidiocarp are made of dikaryotic hyphae
their tips are called called basidia (basidium = singular)
within each basidium karyogamy occurs - two nuclei fuse
followed by meiosis 4 haploid nuclei total per basidium
at the tip of the basidium - each haploid nuclei develops into a basidiospore
basidiospores are released when mature and are carried by the wind – germinate into new mycelia which rapidly undergo more sexual reproduction
PLASMOGAMY
Key
Haploid (n)
Dikaryotic (n + n)
Diploid (2n)
SEXUAL
REPRODUCTION
KARYOGAMY
MEIOSIS
Dikaryotic
mycelium
Basidium containing
four haploid nuclei
Dispersal and
germination
Basidium
1 µm
Mating
type (+)
type (–)
Haploid
mycelia
Gills lined
with
basidia
Basidiocarp
(dikaryotic)
Basidia
Diploid
nuclei
Basidiospore
Basidiospores
basidiospores

27. Fungi as Decomposers
fungi are well-adapted decomposers of organic material
very good at decomposing the polysaccharides cellulose and lignin (plants & wood)
their decomposition makes available to ecosystems inorganic nutrients such as carbon, nitrogen and phosphate ions

28. 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

29. Yeasts
are chemotrophs – convert carbohydrates into CO2 and alcohol (fermentation)
most species are either obligate aerobes (for cellular respiration) or anaerobic (fermentation)
are no species of obligate anaerobes
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
exist as either diploid or haploid forms

30. Yeasts
asexual reproduction through budding or mitosis – occurs in both haploid and diploid cells
sexual reproduction through the production of pheromones by two mating types
two yeast cells of opposite mating types meet and fuse – karyogamy results in a diploid yeast cell
this yeast cell can reproduce asexually by budding
when stressed– the diploid cells undergo meiosis to form spores of two haploid mating types- “alpha” and “a”
Haploid
Diploid
alpha a

31. Fungal Associations
fungi can form mutualistic relationships with plants, algae and animals
Fungal-Plant associations: formation of mycorrhizal associations with the roots of vascular plants
these fungi are called mycorrhizal
all plant species harbor symbiotic fungi called endophytes
these live harmlessly inside the leaves of plants
benefit certain grasses and other non-woody plants by making toxins to deter herbivores
can also increase the plants tolerance to heat, drought or heavy metals
leaf cutter ants depend on fungi to convert
plant material into something these ants can digest

32. Fungal Associations
Fungal-Animal associations: some fungus share their digestive services with animals
assist in the breakdown of plant material
guts of cattle and other grazing mammals
some insects (termites and ants) can raise “farms” of fungi to aid in digestion – called farmer insects
leaf cutter ants depend on fungi to convert
plant material into something these ants can digest

33. Fungal Associations: Lichens
Lichens: 25,000 species
fungus + green algae (or cyanobacteria)
each requires one another to colonize areas they wouldn’t be able to alone
algae provide organic compounds, the cyanobacteria fix nitrogen
algae nestle among the fungal hyphae
found from the arctic to the tropics
most reproduce asexually
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

34. Lichens asexual reproduction: 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
some sexual reproduction can occur through the formation of basidiocarps or ascocarps
Fungal hyphae
Algal cell
Soredia
Algal
layer
Fungal
hyphae
Ascocarp of fungus
10 µm