Chapter 14
Fungi
Importance of Fungi
Together with Heterotrophic bacteria
Ecological decomposers
Decomposing fruit- Rhizopus
Root-rot fungus- white mycelial causes disease in living trees
Acts as decomposers on dead plants
Root rot
Ouch!!!
Fungi
• Composed of Hyphae
• Heterotrophic absorbers
Characteristics of Fungi
• Composed
of Hyphae
Fungal
filaments=
“Cobwebby”
strands of
subterranean
“white stuff”
Mycelium
Fungi form important symbiotic
relationships
• 80% of all vascular plants species from
mutually beneficial associations called
mycorrhizae between roots and fungi
• Plant nutrition
• Lichens form symbiotic relationship with
fungi, algal, or cyanobacterial cells
Four phyla of fungi
• Chytridiomycota
• Zygomycota
• Ascomycota
• Basidiomycota
Chars of Fungi
• All have cell wall
• Cell wall composed of
polysaccharide- chitin
• Chitin more resistant to
microbial degradation
than cellulose
All Fungi Heterotrophic Absorbers
• Unable to engulf small
microorganisms
• Secrete enzymes and
absorb smaller molecules
•Absorb food mostly
at or near the
growing tips of their
hyphae
Fungi obtain their food
• Either as
Saprophytes
or
• As mutualistic
symbionts
Some
• Obtain energy through fermenation
producing ethyl alcohol from glucose (i.e.
yeast)
Fungi reproduce both sexually and
asexually
• Reproduce through the
formation of spores that are
produced sexually or asexually
• Most are nonmotile spores
• Some are dry and small and
airborne
Common method of asexual
reproduction in fungi
By means of spores
• Either produced in sporangia
– The sporangium is a saclike structure, the
entire contents of which are converted into
one or more spores
Asexual reproduction
(Vegetative reproduction)
Or
• Hyphal cells called conidiogenous cells
– Spores produced by conidiogenous cells occur
singly or in chains called conidia
Asexual repro
• Some Reproduce by fragmentation of
their hyphae
Sexual reproduction
• Three distinct phases
• First two are phases of fertilization
(syngamy)
– Plasmogamy- the fusion of protoplasts
– Karyogamy- the fusion of nuclei (some don’t
fuse forming a dikaryon)
The last phase is meiosis
• Sexual reproduction results in the
formation of specialized spores such as
zygospores, ascospores, basidiospores.
Zygospores
• Zygospores
• Asexual and sexual reproduction (by
means of haploid spores)
• Sexually producing zygospores require
two compatible species
Gametangia the gamete producing structures are in the
Process of producing a zygospore
Zygomycetes: Phylum Zygomycota
• Live on decaying plant and animal matter
in soil
• Some are parasites of plants, insects or
small soil animals
• Rhizopus stolonifer- best known
zygomycetes
Life cycle of Rhizopus stolonifer
Zygospore develops within the thick walled zygosporangium
Ascomycetes: Phylum
Ascomycota
Ascomycetes
• Group of fungi
characterized by
their production
of sexual spores
in a sac-like
structure called
an ascus.
“Cup fungus”
Types of Ascomycete
• yeast
• powdery mildew
• cup fungi
– many of these produce spores suited for
airborne dispersion.
The Ascomycota
•Most are blue-green, red and brown molds
that cause food spoilage
• Non motile
•Penicillin
•Form ascospores Internally in Asci
Ascomycetes Eyelash cup, Scutellinia scutellata
Ascomycetes can cause plant
disease
• Brown rot of stone
fruits (Monilinia
fructicola)
•chestnut blight
(Cryphonectria
parasitica)
Dutch elm disease
( Ophiostoma ulmi)
Beneficial Ascomycete
• Many Yeast are also ascomycetes
•Edible Morels and truffles
Edible black truffle,
Tuber melanosporum
spore-bearing structure is
produced below ground
mainly on oaks and
hazelnuts
Edible Ascomycete
Ascomycetes growth
• Most have either unicellular or
filamentous growth forms
• Hyphae have perforated septa
• Hyphal cells of Vegetative mycelim
may be either uninucleated or
multinucleated
Life cycle of an Ascomycete
• Most species undergo asexual
reproduction by the formation of
multinucleated conidia
• Conidia formed from the conidiogenous
cells
• Conidiogeneous cells are borne at the tips
of modified hyphae called conidiophores
“conidia bearers”
Ascomycetes spore development vs.
Zygomycetes spore development
• Unlike zygomycetes which produce spores
internally within a sporangium,
ascomycetes produce their asexual spores
externally as conidia.
Xylaria fungus
Perithecium with ascospores
“Dead mans fingers”
Finger Xsec
Hymenial layer
• Asci usually develop on an inner surface
of the asoma, a layer called the hymenium
or hymenial layer
Hymenium of an ascomycete showing asci with
ascospores section thru the hymenial layer of Morela
Ascomycete life cycle
Basidiomycota
Life cycle of Basidiomycota
As a group, the basidiomycota have
some highly characteristic features,
which separate them from other fungi.
germinate
monokaryons
Single nucleus
Each w/ 1n.
fusion of a hypha with a small spore
simple hyphal fusions
dikaryon
nuclei divide
They are the most evolutionarily advanced fungi, and even their hyphae
have a distinctly "cellular" composition.
• Many
basidiomycota
grow for most of
their lives as
dikaryons, until
environmental
signals induce
them to produce
fruitbodies
• At a late stage of
development, some of
these hyphae produce
special cells termed
basidia (singular,
basidium).
• cells that line the gills
of the common
mushroom are basidia
• Finally, the two
haploid nuclei in
each basidium
fuse - a process
termed
karyogamy) to
form a diploid
nucleus.
• This then
undergoes
meiosis to
produce four
haploid nuclei
• these haploid nuclei migrate
into the basidiospores
• which develop on small
stalks (termed sterigmata)
from each basidium
• The dispersal of these
monokaryotic spores
completes the life cycle.
Basidia on the gills of a toadstool.
Basidiospores
basidium
sterigmata
Basidiospores
Class basidiomycetes
• Hymenomycetes
• Gasteromycetes
Hymenomycetes
Muscimol
Fly agaric Amanita muscaria
Agaricus Bisporus
Portobella
Lentinula edodes
Shiitake
Amanita virosa
lpha-amanitin
Volva
annulus
“Death angel”
Polyporus arcularius
“Shelf fungus”
Ganoderma applanatum
“Fairy rings”
Fruitbodies
“Puffball”
“Puffballs”
peridium
Gasteromycetes
Earth stars
Earthstar
The netted stinkhorn
Gastermycetes
Class Teliomycetes
“Rust”
Blackberrry leaf
“Corn smut”
Ustilago maydis
Hallucinogenic mushrooms
Psilocybe mexicana
Crustose and foliose lichen
Foliose “leafy” lichen
Hummingbirds nest
Witch’s hair
Raindeer moss
Fruticose “shrubby” lichens