2. Class : Ascomycetes (higher fungi)
These are also called sac fungi distinguished by the following characteristics:
(I) Mycelium with septate hyphae.
(ii) Asexual reproduction by conidia is a common feature. They are produced at the apex of the
hyphae called conidiophores.
(iii) Sexual reproduction occurs by producing sac-like structures called asci, each with usually 8
ascospores, produced endogenously.
Figure 14.39 Sexual reproduction in Mucor
(iv) Formation of multicellular complex fruiting body called an ascocarp containing many asci.
(v) Some ascomycetes, like yeast, reproduce by budding also.
The bodies of ascomycetes may be unicellular as in yeast, or multicellular and filamentous as in
powdery mildew. Ascomycetes include yeast, powdery mildew, Claviceps, and most of the blue,
green and brown molds.
Figure 14.40 Yeast
Reproduction : In most Ascomycetes, asexual reproduction takes place by formation of conidia
which are pinched off from the apex of certain specialized hyphae known as conidiophores. e.g.
Penicillim
Sexual reproduction takes place by the formation of ascospores within the asci. Some
ascomycetes are heterothallic (dissimilar mating types) and other are homothallic (similar mating
types). e.g. Claviceps.
Economic importance : Yeast is used for the production of alcohols in brewery, in production
of vitamin B, and for raising bread. Claviceps is used to extract an alkaloid called ergotin which
is used in medicine. LSD is also extracted from an ergot fungus. Some ascomycetes like
Morchella are edible. Neurospora has been used recently for genetic and biochemical research.
Some ascomycetes cause severe plant diseases.
Figure 14.41 Penicillium
Class: Basidiomycetes (higher fungi)
These are also called club - fungi distinguished by the following characteristics:
(I) Mycelium with septate hyphae.
(ii) Asexual reproduction is uncommon.
(iii) During sexual reproduction mycelium develops enlarged reproductive, club-shaped structure
called a basidium, hence the name.
(iv) Each basidium produces 4 basidiospores at the tip outside (exogenously),unlike ascospores
which develop within the ascus..
(v) In some fungi like mushrooms, a multicellular, complex, fruiting body called a basidiocarp
is formed which is often open, sometimes closed. (Basidiocarp = basidia bearing body).
Figure 14.42 Reproduction in Ascomycetes (Claviceps)
Basidiomycetes include large and conspicuous fungi like mushrooms, toadstools, bracket fungi
and puff balls, as well as parasitic forms like rusts and smuts.
Agaricus praeclaresquamosus © Giuseppe Mazza
Boletus satanas © Giuseppe Mazza
Amanita muscaria © Giuseppe Mazza
Amanita phalloides © Giuseppe Mazza
Fistulina hepatica © Giuseppe Mazza
General Structure
With the exception of yeast, all fungi -- from the
microscopic to the very large -- are multi-cellular and
made up of tube-like filaments called hyphae. A
branching network of hyphae is called a mycelium. The
gills, cap and stalk (or stipe) of a large mushroom are
made up of millions of hyphae. Microscopic penicillium
fungus is made up of only a few.
Reproduction
Fungi have a sexual and then an asexual life stage. (In
some fungi, the sexual stage has not yet been
identified.) Spores are asexual structures, which can
grow into new organisms without first fusing with
other reproductive cells. Fungal spores disperse in the
air and develop into a new mycelium if conditions are
suitable.
Conidiophore of Paecilomyces lilacinu
Phungophobe's Phear -- "Higher Fungi"
If you cannot "stomach" mushrooms, then you are a fungophobe and this lecture is likely to be
revolting to you...you have to face your fear here. The higher fungi simply refers to those
organisms commonly placed by taxonomists into Kingdom Fungi.
Zygomycota = Zygomycetes
This division is in Kingdom Fungi and is probably the most primitive of the group. Go over the
life cycle of Rhizopus.
Tell the interesting phototropism and spore dispersal mechanism in Pilobolus.
Ascomycota = Ascomycetes (Sac Fungi)
Show examples starting with yeasts and working up to morels.
Go through life cycle.
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ascospores germinate into haploid mycelium (gametophyte)
one mating type produces ascogonium (female?)
other mating type produces antheridium (male?)
trichogyne of ascogonium touches antheridium and cytoplasms join (plasmogamy)
merged cells become ascogenous hyphae
(dikaryotic, heterokaryotic, septate mycelium)
Is this a sporophyte or what?
haploid mycelium surrounding ascogenous hyphae form ascocarp
tips of ascogenous hyphae form hymenium layer in/on ascocarp
tip cell (the ascus) undergoes karyogamy (union of nuclei to complete syngamy)
this is the ONLY diploid cell (zygote? or just sporocyte?)
ascus undergoes meiosis to make four meiotic products
(after maybe a mitosis to make total of eight products) these are ascospores
Notice how this life history lacks a motile phase!
It is anisogamous at least, but hard to call oogamous.
Asexual reproduction is commonly called the "imperfect" fungi.
In some species it is the only part of the life cycle known. These then are called members of the
Deuteromycota. Deutero- means "duty" and it is the duty of mycologists (those who study fungi)
to learn to identify the sexual stages that belong to these deuteromycetes. A recent example is on
display in the laboratory. The deuteromycete fungi are important for producing industrial
chemicals...penicillin and enzymes for detergents and for "stone washing" blue jeans).
Many ascomycete fungi are the fungal partner in a fungal/algal symbiosis known as lichens. The
ascomycete provides the algal home and a way to survive desiccation and supplies of minerals
from the enviroment, the algae provide carbohydrates for the fungus. It is likely a mutualism.
Bread Mold
Sac Fungi
Club Fungi
Imperfects
Kingdom Fungi
Division Zygomycota
Fungi
Fungi
Fungi
Ascomycota
Basidiomycota
Deuteromycota
# Species 750
chitin
Wall
30,000
25,000
17,000
chitin/glucan
chitin/glucan
chitin/glucan
anisogamous
Isogamous
unknown
Life Cycle zygotic
sporic/kikaryotic
sporic/dikaryotic
unknown
Examples Rhizopus
Saccharomyces
Neurospora
Agaricus
Amanita
Penicillium
Aspergillus
budding
ascus
conidia
ascogonium
antheridium
heterokaryon
hypha(e)
ascocarp
ascospore
mycelium
hypha(e)
dikaryotic
heterokaryon
cap (pileus)
stalk (stipe)
ring (annulus)
cup (volva)
gills (lamellae)
mycelium
basidium
basidiospores
hypha(e)
conidia
mycelium
baking
wine
morels
truffles
cheese
ergot
Dutch elm disease
chestnut blight
ectotrophic
mycorrhizae
LICHENS 20K
mushrooms
puffballs
shaggy manes
Psilocybe
amanitas
rusts
smuts
ectotrophic
mycorrhizae
fairy rings
cheese
antibiotics
'gamy
"isogamous"
Special sporangiophore
Vocabulary rhizoid
stolon
coenocytic
hypha(e)
gametangium
zygospore
Notes:
warm bread
endotrophic
mycorrhizae
ASCOMYCETES