Chapter 31 - Fungi
IV. Kingdom Fungus
A. Estimated 1.5 million species
B. Greek, mycos, fungi (mycelium, mycorrhizae, etc…)
C. Some are single-celled (in general known as yeast), while
most are complex multicellular
D. Fungi are heterotrophs that absorb food after digesting with
enzymes they secrete outside their body called exoenzymes
hyphae
Fig. 17.16
Chapter 31 - Fungi
IV. Kingdom Fungus
E. Types 1. Saprophytes (saprobes, decomposers)
- Break down and absorb nutrients from non-living organic material like
a fallen log, dead animals and organismal waste (feces, etc…)
Fig. 17.16
Chapter 31 - Fungi
IV. Kingdom Fungus
E. Types 2. Parasitic / Pathogens
- Take nutrients from living cells, some pathogenic – 80% of plant
diseases caused by fungus.
“Athletes Foot”
Blithe
Only 50 out of the known 100,000 fungal species are parasites of animals and these do relatively little damage.
Chapter 31 - Fungi
IV. Kingdom Fungus
E. Types 2. Parasitic / Pathogens
- Of the 100,000 known fungal species, 30% are parasites mostly of
plants:
- Between 10% and 50% of world fruit harvest lost each year to fungus
Chapter 31 - Fungi
IV. Kingdom Fungus
E. Types 3. Mutualistic symbionts
- mycorrhizae
mycorrhizael
hyphae
Fig. 17.16
Chapter 31 - Fungi
IV. Kingdom Fungus
F. Body Structure
1. Multicellular fungus
- Hyphae - Network of tiny filaments making up body of fungus
- Cell walls are made of… Chitin = polysaccharide of
modified glucose also
found in exoskeletons of
insects and crustaceans
(arthropods)
- Mycelium (plural, mycelia) – entire interwoven mass of hyphae
- High surface area to volume ratio, efficient feeding
- 1ml of soil may contain 1km of hyphae
- Like plants, hyphae need to GROW through environment
Fig. 17.16
Chapter 31 - Fungi
IV. Kingdom Fungus
F. Body Structure
1. Multicellular fungus
- Structure of Hyphae
a. Septate hyphae - Most fungi have
hyphae divided into cells by septa
(crosswalls) with large pores for sharing
material
b. Coencytic hyphae – continuous
cytoplasm with many, many nuclei due to
repeated mitosis without cytokinesis similar
to slime molds.
Fig. 17.16
Chapter 31 - Fungi
IV. Kingdom Fungus
F. Body Structure
1. Multicellular fungus
- Structure of Hyphae
c. There are hyphae adapted for trapping
and killing
d. Haustoria – specialized hyphae that
can penetrate host cells.
Fig. 17.16
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
1. Produce spores either
sexually or asexually
- Carried by wind or water
- We see this when we leave food
out or in fridge too long…spores
are everywhere in the air….
Puffball mushroon exploding releasing trillions of spores
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
- Many, but not all reproduce both
sexually and asexually. Some do one
or the other.
- nuclei of hyphae and spores are haploid.
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
Sexual reproduction
- Begins when two distinct mycelia of
different mating types secrete
pheromones that bind to receptors on
each others surfaces.
- Hyphae then move toward each other
(source of pheromone) and fuse =
plasmogamy.
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
Sexual reproduction
- Haploid nuclei do not fuse right away
in many fungi resulting in mycelia with
genetically different nuclei =
heterokaryon (“different nucleus”).
- Dikaryotic mycelia – if heteronuclei
pair off two to a cell.
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
Sexual reproduction
- Hours, days or years may pass until
karyogamy (fusion of nuclei) occurs
resulting in only diploid stage.
- Meiosis follows karygomy restoring
haploid mycelium and more spores will
be made by mitosis.
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
ASexual reproduction
- Clones made by mitotic cell division
of specialized cells in mycelia to form
spores…which undergo mitosis to
make new mycelia.
Chapter 31 - Fungi
IV. Kingdom Fungus
G. Life cycle of fungi
2. General life cycle of fungus:
Molds
- Any multicellular fungus that can
reproduce rapidly and asexually. It is a
general term. Many of these fungi can
reproduce sexually, but mold refers
only to the asexual stage.
Deuteromycetes (aka imperfect fungi)
- Molds or yeasts with no sexual stage.
Yeast
- Reproduce predominantly asexually
not by using spores, but by budding, a
type of simple form of cell division.
Sometimes they reproduce sexually.
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
The five major phyla of fungi:
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
1. Chytridiomycota (Chytrids)
- Found in lakes and soil, some
saprobes others parasitic
- First to diverge
- Unique from other fungi in that their
spores have flagella called zoospores.
As you would expect if common
ancestor were flagellated protist…
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
2. Zygomycetes
- 1000 known species
- Fast growing molds that rot produce
like fruit and bread…
- Other live as parasites or commensal
on animals
- Characterized by presence of
sexually produced heterokaryotic
zygosporangium
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
2. Zygomycetes
Life cycle of black bread mold
Goes sexual when environmental
condition deteriorate like food scarce
forming zygosporangia.
zygosporangia
Resistant to freezing and drying and
are metabolically inactive.
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
3. Glomeromycetes
- 160 species known
- All form endomycorrhizae called arbuscular mycorrhizae
Arbuscule
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
4. Ascomycetes
- 32,000 species
- Production of sexual spores in saclike asci
- Therefore commonly called sac fungi
- Vary from unicellular yeast including bread/beer/wine making
yeast (Saccharomycetes cerevisiae) to cup fungi and morels
- Consist of some of most deadliest plant pathogens
making them relevant to agriculture
- More than 40% are lichens – mutualistic relationship between
fungi and unicellular chlorophytes (green algae) or with
cyanobacteria.
- Others form mycohorrhizae
Lichen growing on a tree:
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
4. Ascomycetes
- lichen:
The fungus can reproduce sexually
as will be discussed via the ascocarp,
while the algae will reproduce
asexually.
The fungus can also reproduce
asexually if fragments called Soridia
break off becoming a new lichen after
many round of mitotic division.
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
4. Ascomycetes
- Neurospora crassa
i. Best studied ascomycete
ii. A common bread mold
iii. Life cycle:
Conidia = asexual spores
Ascospores are within asci, which are within the ascocarp
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
5. Basidiomycetes
- Club fungi
- 30,000 species
- Named after the basidium (little
pedestal) – a cell in which a transient
diploid stage occurs.
- Important decomposers (best fungi at
breaking down lignin), some form
mycorrhizae, others are plant parasites
- Toad stools
Chapter 31 - Fungi
IV. Kingdom Fungus
H. Fungi Evolved from a single-celled flagellated protists
5. Basidiomycetes
- Life Cycle
Chapter 31 - Fungi
IV. Kingdom Fungus
A. Fungus
hyphae