FUNGUS KINGDOM LECTURE NOTES
DR. SUSAN PETRO
Fungi (funj'-eye) means “sponge”
I. Definition
Eukaryotic, absorptive heterotrophs with chitin cell walls and no embryonic
stages
II. Origin of Fungus Kingdom
A. Aquatic ancestor as did the plants and animals
B. Fungi share a common ancestor more recently with animals than with plants
1. Store carbohydrates as glycogen as do animals
2. Ribosomal RNA base sequences more similar to those of animals
3. Amino acid sequences of actin and tubulin (cytoskeleton proteins),
enolase (glycolytic pathway enzyme) and elongation factor (protein
synthesis enzyme) are more similar between animals and fungi than
between plants and fungi
C. Possible phylogenetic tree
Fungi
Choanoflagellates
Animals
Common protist ancestor
III. Morphology
A. Unicellular
Yeasts and some chytrids
B. Multicellular
• Filamentous body form
• Filaments called hyphae (means “web”)
• A mass of hyphae is called a mycelium
• This type of body form has a large surface area to volume ratio so
more area for absorption of nutrients
• Hyphae can be coenocytic (means “shared” “cell”) many nuclei in
one cell – a result of mitosis (division of the nucleus) without
cytokinesis (division of the cytoplasm)
1
•
Hyphae can be septate – walls
between cells, but walls have
a pore so are perforate and
material can move rapidly
from one cell to the next
IV. Nutrition
A. Saprobes – dead organic material
• Primary decomposers along with bacteria
• Can digest cellulose and lignin
• May be very specific e.g. one species only grows on pine needles,
another only on horse dung
• Example of saprophytic fungus – mushrooms from store
B. Predatory
Nematode - trapping fungi (nematodes are a type of small worm)
Use nematodes as a nitrogen source
C. Symbiosis – two types of organism living together
1. Parasitism – one partner benefits the other is harmed
a. Plant parasites
e.g. Dutch elm disease, chestnut blight, wheat rust, corn
smut
b. Animal parasites
Athlete’s foot
Ringworm (to right)
Blastomycosis
Coccidioidomycosis
2. Mutualism – both partners benefit
a. with animal kingdom
• With leaf cutter ants – ant and fungus are not found
separately. The fungus breaks down cellulose so
the ant can use it as an energy source while the ant
provides leaves for the fungus and maintains a pure
2
fungal culture ‘weeding’ out any other species of
fungi that might compete.
•
With ruminants e.g. cows, sheep, goats etc.
The chytrid, Neocallimastix, digests cellulose so the
cow can use it as an energy source and the cow’s
rumen provides constant environmental conditions
and a food source (ingested plant material) for the
chytrid.
b. with protist (green algae) and bacteria (cyanobacteria)
kingdoms
Lichens “Ah gee, you’re a fun guy, I’ve taken a liken’
to you.”
• Green algae and cyanobacteria are photosynthetic
and make sugars they share with the fungus
• Fungus absorbs water and minerals for algae or
cyanobacteria
• Can live where neither one could live alone. Are
the first colonizers of bare rock
• 90% of plants have this relationship, even found in
the thallus of liverworts which lack roots
c. with plant kingdom
Mycorrhiza - “fungus” “root”
• Plants and fungi became terrestrial together
• Fungus increases the surface area for water
absorption and also increases the mineral absorption
of Zn, Cu, Mn, N and P (10 times more P absorbed
when mycorrhizae are present than when they are
lacking)
• Plant photosynthesizes and produces sugars for the
fungus
• Trees transplanted to mineral-rich plains die of
mineral deficiencies without mycorrhizal fungi
• Orchids won’t germinate without mycorrhizal fungi
since the tiny seeds have no food supply – fungus
provides food as a saprophyte to orchid embryo
until it produces a leaf for photosynthesis
3
V. Growth and Reproduction
A. Asexual Reproduction
1. Fragmentation
2. Budding – unequal cytokinesis – yeast
3. Asexual spores
B. Sexual Reproduction
Fungi are differentiated by the structures
formed in sexual reproduction
Yeast budding
VI. Generalized Fungal Life Cycle compared to Generalized Plant and
Animal Life Cycles
Fungus Kingdom
• In the majority of members of this kingdom only one cell, the zygote, is
diploid (2n), the vegetative part of the life cycle is 1n
• Zygote undergoes meiosis to form 1n spores
4
Plant Kingdom
• Multicellular 1n and 2n stages – alternation of generations
• Cells in 2n sporophyte generation undergo meiosis to form 1n spores which
divide by mitosis to form the 1n gametophyte which produces 1n gametes.
• Gametes fuse (fertilization) to form the 2n zygote which divides by mitosis to
form the 2n sporophyte.
Animal Kingdom
• Only one cell, the gamete, is haploid (1n)
• Meiosis occurs in reproductive organs to produce the gametes
• Two gametes fuse (fertilization) to form the 2n zygote which divides by
mitosis to form all other cells that make up the body.
VII. Five Phyla (divisions) of the Fungus Kingdom – Classified by
Method of Sexual Reproduction Primarily
A. Chytridomycota – “mycota” - fungus
1. Differences from other fungal phyla
• Reproduce by means of flagellated gametes and spores
Flagellum
• Most are aquatic unlike all other groups (so like fungus ancestor)
2. Similarities to other fungal phyla
• Similar lifestyle - absorptive heterotrophs
• Similar morphologies – unicellular and filamentous types
• Chitin cell wall
• Molecular evidence – ribosomal RNA
3. Examples of chytrids
• Neocallimastix – mutualistic, obligate anaerobe in rumen of cows (see
above)
• Batrachochytridium dendrobatidis – frog-killing chytrid – effects
exacerbated by environmental stress
5
B. Zygomycota – “zygos” Greek for linked together or joined
1. Sexual reproduction
Hyphae fuse to form a zygospore
2. Morphology
Coenocytic – cells with many nuclei
3. Example
Black bread mold
C. Glomeromycota
1. Formerly considered zygomycetes, but DNA evidence puts them in their
own monophyletic group
2. Only reproduce asexually
3. All glomeromycetes form a distinct type of endomycorrhizae called
arbuscular (word means tree - see shape in photo below) mycorrhizae
4. About 90% of all plants have such symbiotic partnerships with
glomeromycetes
Plant cell wall
Fungal hyphae inside plant cell wall
D. Ascomycota – sac fungi – asco means sac – largest phyla
1. Sexual reproduction
Fusion of hyphae and formation of a fruiting body
Fruiting body produces sacs where zygotes are formed by fusion of nuclei
and where zygotes then undergo meiosis to produce ascospores
8 Ascospores in ascus
2. Morphology
Some are unicellular (yeasts)
6
Hyphae septate and perforate
3. Examples
a) Foods produced by ascomycetes
• Camembert and Brie cheeses – rind is hyphae
• Blue cheeses – Roquefort (name limited by French
regulation to cheese made in caves in Roquefort from
sheep’s milk.), Stilton (English), gorgonzola (Italy from
cow’s milk)
• Soy sauce
• Citric acid for sodas etc.
• Processing of cocoa beans for chocolate
• Wine and beer fermentation and bread making
b) Edible ascomycetes
Truffles
• Truffles are the underground spore-producing structures of
an ectomycorrhizal fungus that is associated with oaks
•
Truffles
Truffle pig at work
Strong odor so insects and mammals will excavate to
spread the spores – French use truffle pigs and truffle
hounds to locate them.
• One variety has brought up to $1,500/pound
c) Plant parasites
Dutch elm disease – from Asia via Holland in 1919
Chestnut blight – Wiped out the American chestnut
Ergot of rye (air' got) means spur such as roosters have
Convulsions, hallucinations, gangrene – contains LSD, a
7
hallucinogen, and ergotamine, a vasoconstrictor,
• Salem witch trials
• Peter the Great’s failure to gain a seaport on Black Sea in
1722 from Turkey
d) Antibiotic producers
e) Clothing processors - produce the cellulases used by clothing
manufacturers to give jeans the stone-washed look
E. Basidiomycota – club fungi – basidio means club
1. Sexual Reproduction
Fusion of hyphae and formation of a fruiting body
Produce basidia, club-shaped structures, that produce basidiospores
Basidiospores
Basidium
2. Morphology
Septate and perforate
3. Physiology
Only organisms on earth that can digest lignin completely to CO2,
can’t use as an energy source but gives access to cellulose
4. Examples
• Mushrooms, puffballs and bracket fungi
The largest living organism ever found is a honey mushroom,
Armillaria ostoyae. Its hyphae cover 3.4 square miles of land in
eastern Oregon and it’s still growing!
• Rusts and smuts
Wheat rust, white pine blister rust, corn smut
Coffee rust – 1875 Sri Lanka – growers had cut down trees that would
shelter from monsoon winds so spores could blow from one plant to the
next
Coffee rust
Corn smut
8