Download 7 Notes (Kingdom Fungi).

Biology 110, Section 11
J. Greg Doheny
October 4th, 2013
KINGDOM FUNGI
Quiz Questions:
1. What is the main polysaccharide constituent of fungal cell walls?
2. What is the main polysaccharide constituent of arthropod exoskeletons?
3. List one major polysaccharide that gives wood (and other plants) structural support.
4. What is a lichen?
5. What is an aflatoxin?
6. What is the name for a fungal colony that contains both algae and fungi living in a
mutualistic relationship?
7. What is the name for fungi that live in close symbiotic relationship with plant roots?
8. What is the name for a mass or colony of fungal hyphae (What do you call the main
body of a fungal colony)?
9. What is the name of the long, single-celled filaments that fungi make?
10. What is the name for a specialized fungal hyphae that can penetrate live cells, and
extract nutrients from them?
11. What is the name for small chemical molecules designed to attract someone (or
something) of the opposite sex for purposes of sexual reproduction?
New Words!
 Arbuscule: Hyphae formed by fungi (usually glomeromycetes) that can enter root cells
of plants, and form tree-like structures designed to exchange nutrients with plant roots.
 Arbuscular mycorrhizal fungi: fungi whose hyphae can penetrate plant roots and other
living tissues.
 Ascocarp: a large, elaborate fruiting body (‘mushroom cap’) produced by ascomycetes.
 Ascus (plural: Asci): the sack-like container that contains the sexual spores of an
ascomycete fungus. Asci can be microscopic and simple, or very large and elaborate,
depending on the species of ascomycete.
 Basidiocarp: large ‘cap’ structure fruiting body produced by the basidiomycetes.
 Cellulose: a polysaccharide that is one of the main constituents of both soft and hard
plants, including wood.
 Chitin: a polysaccharide that is one of the main constituents of the fungal cell wall, and
also the main constituent of arthropod exoskeletons.
 Coenocytic hyphae: Hyphae where individual cells are not separated by septa. (Giant
‘super cell’)
 Ectomycorrhizal fungi: fungi that live on plant roots without penetrating them.
 Endophyte: a symbiotic fungus living inside a plant, sometimes producing toxins that
discourage herbivores and insects from eating the plant.
 Haustoria: specialized hyphae capable of penetrating live cells and extracting nutrients.
 Heterokaryon: a cell (or super cell) containing two different nuclei.

















Heterokaryotic stage: stage in fungal sexual reproduction where hyphae from two
different fungi have fused to contain two different types of nuclei, but the different
nuclei remain separate.
Hypha (hyphae): fungal filaments made of single cells.
Karyogamy: fusion of the different nuclei in a heterokaryon to form a temporary diploid
zygote.
Lichen: a colony of fungi and algae growing in a symbiotic relationship. (Often
resembles a green plant.)
Lignin: a polysaccharide that is one of the main constituents of wood.
Meiosis: a type of cell division that results in a reduction in the number of copies of the
genome present. Cells divide without copying the genome first. (Example: diploid
humans producing haploid sperm or eggs [gametes] using meiosis.)
Mitosis: Cell division where the genome is copied first, so there is no reduction in the
number of copies of the genome. (Example: division of skin cells to produce more skin
cells. The diploid skin cells copy the genome first, so that there are actually FOUR copies
of the genome present just before cell division. The cell then divides to give two diploid
daughter cells.)
Morel: An ascomycete that produces its ascocarp above ground.
Mycelium: large interwoven mass of fungal hyphae
Mycorrhizae: Fungi that live in mutualistic or parasitic symbiosis with plants (usually
with roots).
Pheromones: chemical signals that attract the hyphae of two different mating type
fungi to one another.
Plasmogamy: fusion of fungal hyphae with mixing of the cytoplasms, but no fusion of
nuclei.
Septum (septa): cell walls dividing cells in a hypha.
Septate hyphae: Hyphae where the cells are separated by septa.
Soredia: a small entangled mass of fungal hyphae and algae cells used to disperse a
lichen.
Sporangium: the hard, round, black, microscopic fruiting body produced by
zygomycetes.
Truffle: An ascymycete that produces an ascocarp underground.
NOTES: Kingdom Fungi
Fungi: Single-celled heterotrophs (decomposers) that either do not form multicellular
structures (ie-yeast), or form only very simple multicellular structures (ie-mushrooms). The
main multicellular structure of fungi is the hypha, a thin thread or filament composed of
individual fungal cells. Fungi differ from plants (and some protists) in that A) they are not
photosynthetic (although many protists are not photosynthetic), and B) their main structural
polysaccharide is chitin, not cellulose. This is convenient because fungi ‘eat’ dead wood by
secreting enzymes that break cellulose and lignin down into simpler sugars which their hyphae
can then absorb. These enzymes (called cellulase and lignase enzymes, respectively) do not
break down chitin, despite the fact that chitin has a structure very similar to cellulose. (Note,
the exoskeletons of arthropods are also made of chitin.) When we do the microbiology lab,
you’ll find that most of the microbes you find growing on PAPER MONEY are fungi. This is
because cellulose is the main constituent of paper.
Yeast vs. Fungi: Yeasts (like the baker’s yeast Saccharomycies carevisiae) are single-celled
versions of fungi. Fungi are essentially just yeast cells that form filaments (hypae) and
occasionally more complicated structures (‘fruiting bodies’ etc.). Interestingly, however, most
fungi are dimorphic (having two forms or arrangements), living as single cells at higher
temperatures (ie-37®C, or ‘body temperature’) and multicellular hyphae at lower temperatures
(ie-23®C, or ‘outdoor temperature’).
At low (ambient) temperatures, a fungus usually forms a complicated network or mass of
hyphae called a mycelium. Depending on the species of fungi, fungal mycelia can range in size
from very small to very large. The round, ‘powdery’ looking blue colonies you see on moldy
bread are small fungal mycelia (Example: Rhizopus stolonifer). The mushrooms you see in the
forest are only the surface parts of a massive underground mycelium, which could extend
underground for several acres (Example: Armillaria ostoyae).
Fungal hyphae: Some fungi form septate hyphae, where individual cells are separated by walls
called septa (singular septum). Other fungi form coenocytic hyphae, where there are no septa
between cells, and the mycelium is essentially one giant ‘super cell.’ (This is analogous to
cellular slime molds vs. plasmodial slime molds.) Some fungi live primarily on dead materials
(usually dead wood or leaves), some fungi are mutualistic, and others are parasitic. Parasitic
and mutualistic fungi form special types of hyphae called haustoria, which are able to
penetrate plant cell walls, and extend inside to extract nutrients from live (rather than dead)
plants (Figure 31.4). Fungi that live in either mutualistic or parasitic symbiosis with plants are
called mycorrhizae. Arbuscular mycorrhizal fungi actually penetrate root cells, while
Ectomycorrhizal fungi merely form a network of filaments around the surface of roots. (Some
haustoria can also penetrate lung tissue and grow in human lungs when fungal spores are
inhaled, leading to serious lung infections.) Mycorrhizae are important because many plants
cannot synthesize nitrogen compounds (like amino acids) from nitrogen in the atmosphere, and
survive by living in mutualistic relationships with fungi that can.
Sexual and asexual reproduction in fungi: Humans spend most of their lives as diploid (2n)
organisms, with a transient haploid (1n) phase. We live as diploids, but make haploid gametes
(sperm and eggs) using a special type of cell division called meiosis (to be discussed later).
Fungi, and many other organisms do the opposite, living primarily as haploid organisms, but
having a transient diploid phase during mating. Diploid cells resulting from a mating of two
haploid fungi then undergo meiosis to produce haploid spores which are dispersed by the wind
to form new fungal colonies elsewhere.
Asexual reproduction: Fungi simply make haploid spores that are carried away by the wind and
germinate elsewhere. Spores are formed in the tips of hyphae.
Sexual reproduction: Most fungi have a set of genes that determine one of two ‘mating types.’
Fungi of one mating type or the other are virtually identical, but are driven to undergo sexual
reproduction if fungi of different mating types are found close together. Fungi are also capable
of switching mating types. When two different mating types are close to one another they
secrete pheromones that attract each others’ hypae. Hyphae from the two different fungi will
grow towards each other, and then fuse together. Cell nuclei from each fungus will then mix in
a common cytoplasm, but the nuclei have not yet fused together. This is known as
plasmogamy. The genomes from the two fungi have not mixed, just the cytoplasms of the cells
containing the nuclei. With two different types of nuclei sharing the same cytoplasm, the
fungus now enters what’s known as a heterokaryotic stage. (‘Heterokaryon’ means ‘two
different nuclei,’ and a hyphae or cell containing two different types of nuclei is called a
heterokaryon.) Eventually the different types of nuclei will fuse (a process called ‘karyogamy’)
forming temporary diploid cells (zygotes), and allowing for re-arrangement of the DNA. The
temporary zygotes then undergo meiosis to form haploid spores that contain haploid genomes
that are slightly different form either of their parents. In the case of sexual reproduction, the
spores are usually put into a special container called a fruiting body. The fruiting body is
usually elevated above the mycelium on a stalk (small stem).
Thus, sexual reproduction in fungi goes as follows: Fusion > Plasmogamy > Karyogamy forming
zygotes > Meiosis forming haploid spores > deposition of spores into a fruiting body, and
dispersal of spores from the fruiting body into the air. In some cases the fruiting body can be
large, colourful and elaborate (ie-mushroom caps).
Evolutionary history of fungi: Recall from the last notes set that one of the groups of protists
was a clade called the Unikonta, which was composed of two separate clades, the
Amoebozoans and the Opisthokonts. The Opisthokonts are descendants of a common,
unicellular flagellated protist, and many of its descendants still have a flagellated stage (ieflagellated sperm in humans, and the Chytrid fungi). One branch of the clade evolved into the
animals and another into the fungi. One branch of the fungal clade, the Chytrids, is the only
fungi to retain its flagellated spore form. Other fungal spores do not have flagella.
Major Phyla of the Fungal Kingdom:
1. Chytridiomycota (The Chytrids): Do not form large colonies. Often live as parasites or
mutualists in the digestive tracts of animals or insects. (Cows can digest grass, made of
cellulose, partly because of mutualistic chytrids living in one of their stomachs. Protists
and bacteria capable of digesting cellulose also live there. Fung, protists and bacteria
capable of breaking down cellulose also live in the guts of insects like termites.) Chytrids
produce flagellated spores called zoospores.
2. Zygomycota (The Zygomycetes): Fast growing molds that often cause food spoilage (ieblack bread mold Rhizopus stolonifer. The black appearance is actually the microscopic,
black fruiting body, which is full of sexual spores.) Zygomycota produce hard, round,
black fruiting bodies called sporangia (singular: sporangium). Some amazing
zygomycota can actually aim their sporangia towards the light, and fire their spores
towards light.
3. Glomeromycota (The Glomeromycetes): (Have you ever heard the expression to
‘GLOM’ onto something?) Glomeromycetes are the main type of fungi that forms
mutualistic relationships with plant roots. About 90% of plant species live in mutualistic
relationships with glomeromycetes, with the fungi providing the plant with nitrogen
compounds and the plant providing the fungi with carbohydrates and other nutrients.
Glomeromycetes form special hyphae called arbuscules that push inside root cells and
form tree-like structures designed to exchange nutrients.
4. Ascomycota (The Ascomycetes): Main feature of the ascomycetes is that they place
their sexual spores into a sack-like structure called an ascus. A number of asci are then
placed into a fruiting body. Depending on the species of ascomycete, the fruiting body
can be microscopic and simple, or large and elaborate. Large, colorful fruiting bodies
are called ascocarps (Figure 31.16). Many of the things we commonly call ‘mushrooms’
are the ascocarps of ascomycetes. Morels and Cup Fungi are two types of ascomycetes
that grow in soil, but produce their ascocarps above ground. Truffles are ascomycetes
that grow in soil but produce their ascocarps below ground (ie-pigs digging for truffles to
eat at the roots of trees). Ascomycetes also produce large numbers of asexual spores
(spores that aren’t produced as a result of a mating with another fungus) called conidia
at the ends of specialized hyphae called conidiophores (Figure 31.6). Conidiophores
usually look like ‘fingers’ at the ends of branched hyphae, and are not elaborate like
ascocarps.
Many ascomycetes live in symbiotic relationships with green algae to form things called
lichens (discussed below). Other ascomycetes live as symbiotic endophytes inside plant
leaves. Many ascomycetes have been used as model organisms by scientists to study
how mitosis and meiosis work (Example: Neurospora crassa). Many other ascomycetes
are used in the pharmaceutical industry to produce drugs and antibiotics (Example:
Penicillium chrysogenum produces the antibiotic penicillin!).
5. Basidiomycota (The Basidiomycetes): This phylum contains most of the fungi we
commonly think of a ‘mushrooms.’ Includes three types of fungi commonly called
‘mushrooms’ (the classic ‘capped mushroom’ shape), ‘puffballs’ and ‘shelf fungi.’ Often
seen in the forest growing on dead logs. Produce large, colourful fruiting bodies called
basidiocarps, with many gills underneath. Gills are simply a folding of the surface
containing the basidiospores (specific name for spores made by basidiomycetes),
designed to increase the surface area.
FUNGI AS SYMBIONTS
Fungi-Plant Mutualism: in addition to the relationships mycorrhizae form with plant roots,
some fungi also form endophytes, or fungi (usually ascomycetes) living inside the leaf cells of
plants. Endophytes sometimes produce toxins which discourage herbivores and insects from
eating the leaves.
Fungi-Animal Mutualism: Many animals and insects that eat either grass or wood (ie-cows and
termites) have symbiotic fungi living in their guts (usually Chytrids) that produce cellulase
enzymes. Without these symbiotic fungi (as well as some symbiotic protists and bacteria) these
animals would not be able to digest cellulose-containing plant materials. Some insects like leafcutter ants cut up plant leaves and then take them back to their nest and allow the leaves to be
broken down by fungi. The ants then eat the fungi. Thus, the ants are ‘fungi farmers!’
Fungi-Algae Mutualism: some fungi (usually ascomycetes) form a symbiotic relationship with
photosynthetic green algae, where the fungal mycelium is mixed together with photosynthetic
algae to form amazing colonies called lichens that can grow on many surfaces where nothing
else can grow (ie-rock surfaces). Much of the growth on rocks located near the ocean is
actually lichens, though they are often mistaken for mosses (non-vascular plants) growing on
rocks. The fungal mycelium provides the algae with a moist place to live on land, and the algae
provide the fungus with nutrients from photosynthesis. Depending on the shape of the
mycelium made by the fungi in question, the lichen can have a mold-like appearance (a
crustose lichen), a leaf-like appearance (a foliose lichen), or a moss-like or shrub-like
appearance (a fruticose lichen). Lichens are dispersed when soredia (small entanglements of
fungal hyphae and algae cells) break off and are carried elsewhere by wind.
Fungi as parasites and pathogens: Many fungi spoil agricultural crops by growing on corn and
wheat. Corn Smut is caused by a basidiomycete called Ustilago maydis, and the poisonous
ergots that grow on wheat are caused by a genus of ascomycetes called the Claviceps genus
(Example: Claviceps zizaniae). Also, many fungi produce powerful toxins called aflatoxins that
cause liver cancer (example: Aspergillus flavus, an ascomycete that causes spoilage of corn and
peanuts). Finally, a number of fungi can live on or in humans causing diseases called mycoses
(singular: mycosis). Athletes foot and scalp ringworm are examples of fungal mycoses. Both
are caused by an ascomycete genus called Trichophyton.
PRACTICE QUESTIONS:
Match the term to the definition:
a. Arbuscule
b. Ascocarp
c. Ascus
d. Basidiocarp
e. Cellulose
f. Chitin
g. Coenocytic
h. Conidia
i. Endophyte
j. Fruiting body
k. Haustoria
l. Heterokaryon
m. Hypha
n.
o.
p.
q.
r.
s.
t.
u.
v.
w.
x.
y.
z.
Karyogamy
Lichen
Lignin
Morel
Mycelium
Mycorrhizae
Pheromone
Plasmogamy
Septum
Soredia
Sporangium
Truffle
Zoospore
1. A flagellated spore formed by a Chytrid.
2. Small sack or tube-like container holding the sexual spores of an ascomycete.
3. Name for the thin, single-celled filaments produced by fungi.
4. Name for the classic ‘mushroom cap’ formed by basidiomycetes.
5. Name for small chemical molecules secreted by an organism to attract a mate.
6. Hard, round, microscopic container holding the sexual spores of a zygomycete.
7. Specialized hyphae that penetrate the cells (usually the roots) of live plants (or animals).
8. Common name for the underground ascocarp produced by a species of ascomycete.
9. Name for asexual spores produced by ascomycetes.
10. Special hyphae formed by glomeromycetes to penetrate the roots of plants that they
are living in mutualistic relationships with.
11. Colourful, elaborate fruiting body made by some species of ascomycetes.
12. Wall that divides cells in a hyphae.
13. Name for a cell that contains two separate nuclei.
14. Polysaccharide that is the main constituent of fungal cell walls, as well as arthropod
exoskeletons.
15. Term used to describe fusion of haploid nuclei during fungal mating.
16. A mutualistic colony of fungi and algae.
17. Two polysaccharides that form the main structural support for plants.
18. Name for the network of hyphae that form the body of a fungal colony.
19. Fusion of fungal hyphae and cytoplasm during mating, preceding fusion of nuclei.
20. Name for fungi that live in a mutualistic relationship with plant roots (usually
glomeromycetes).
21. Common name for an above ground ascocarp produced by an ascomycete.
22. Small entangled mass of fungal hyphae and algae used to disperse a lichen.
Listed below are the five major Phyla of fungi. Match the Plylum to the description.
a.
b.
c.
d.
e.
Chytrids
Zygomycetes
Glomeromycetes
Ascomycetes
Basidiomycetes
1. Contains most of the fast-growing molds responsible for food spoilage. (Example: the
black bread mold Rhizopus stolonifer.)
2. Fungi that produce flagellated spores called zoospores.
3. Fungi that form most of the mutualistic relationships with plant roots.
4. Fungi that produce round, black fruiting bodies called sporangia.
5. Contains the genus Penicillium, a fungus used to make the antibiotic penicillin.
6. Fungi that produce arbuscules.
7. Phylum that contains ‘mushrooms’ known as morels, cup fungi, and truffles (but do not
look like the classic ‘capped’ mushrooms).
8. Contain the fungi responsible for athletes foot and scalp ringworm (Genus
Trichophyton).
9. Type of fungi that live inside the guts of animals and insects, allowing them to digest
cellulose.
10. The type of fungi that are usually found in lichens, living in a mutualistic relationship
with algae.
11. Usually seen growing in the forest on damp, dead logs, this phylum contains most of the
classic ‘mushrooms’ that make large caps with gills.
Essay type questions:
1. What are mycorrhizae, and why are they important to plants and agriculture?
(Paragraph form, one page only, 10 points)
2. How do fungi obtain nutrients, and how is the morphology of hyphae advantageous (an
advantage) to this? (Paragraph form, one page only, 10 points)