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IV. Fungi KNOW RED STUFF
A. Overview
1. General Characteristics
- multicellular eukaryotes
- heterotrophic
- absorptive nutrition:
excrete enzymes into
environment and absorb the
product of that digestion. They
digest dead matter (decomposers)
or live matter (pathogens), or may
be symbiotes.
IV. Fungi
2. Classification
- Chytridiomycota
- Zygomycota
- Ascomycota
- Basidiomycota
Single celled members of these groups are all called
“yeasts”. They are distinguished from protists based on a
chitinous cell wall and absorptive (rather than phagocytic)
nutrition.
IV. Fungi
3. General Biology
- The organism is composed of threadlike “hyphae”
IV. Fungi
3. General Biology
- The organism is composed of threadlike “hyphae”
- The hypha can be coenocytic (without divisions)
or septate (with incomplete cell walls between)
IV. Fungi
3. General Biology
- The organism is composed of threadlike “hyphae”
- The hypha can be coenocytic (without divisions)
or septate (with incomplete cell walls between)
- These have a huge surface area/volume ratio
for absorption.
- The largest organisms known… 37 acres.
IV. Fungi
4. Ecological Roles
- decomposers: Fungi decompose lignin and cellulose,
which most free-living bacteria can’t digest.
IV. Fungi
4. Ecological Roles
- decomposers: Fungi decompose lignin and cellulose,
which most free-living bacteria can’t digest.
* antibiotics
IV. Fungi
4. Ecological Roles
- decomposers: Fungi decompose liginin and cellulose,
which most free-living bacteria can’t digest.
* antibiotics
- mycorrhizae: fungal symbiotes of certain plants. The fungus
increases the absorbance area of roots dramatically, and passes
water and nutrients to the plant. The plant feeds the fungus
with glucose.
IV. Fungi
4. Ecological Roles
- decomposers: Fungi decompose liginin and cellulose,
which most free-living bacteria can’t digest.
* antibiotics
- mycorrhizae: fungal symbiotes of certain plants. The
fungus increases the absorbance area of roots dramatically, and
passes water and nutrients to the plant. The plant feeds the
fungus with glucose.
- lichens – symbiote with alga
IV. Fungi
4. Ecological Roles
- decomposers: Fungi decompose liginin and cellulose,
which most free-living bacteria can’t digest.
* antibiotics
- mycorrhizae: fungal symbiotes of certain plants. The fungus
increases the absorbance area of roots dramatically, and passes
water and nutrients to the plant. The plant feeds the fungus
with glucose.
- lichens – symbiote with alga
- pathogens – Athlete’s foot, ringworm, yeast infections
- parasites – entomophagous fungi
IV. Fungi
B. Zygomycetes
- coenocytic hypha
- asexual reproduction haploid
hypha produces sporangia and
releases spores.
IV. Fungi
B. Zygomycetes
- sexual reproduction –
hypha touch, and produce
gametangia. Gametes
produced inside – fusion into
dikaryotic cells (2 nuclei).
Each dikaryon then becomes
diploid (fusion of nuclei and
undergoes meiosis. Spores are
released.
- many are imporant
mycorrhyzal symbionts.
IV. Fungi
C. Ascomycetes
- septate hypha
IV. Fungi
C. Ascomycetes
- septate hypha
- characterized by production of
spore-bearing “asci”
IV. Fungi
C. Ascomycetes
- septate hypha
- characterized by production of
spore-bearing “asci”
- baker’s yeast
(levening and fermentation)
- molds – pathogens of plants
such as Aspergillus, Penicillium,
Neurospora, Chestnut Blight,
Dutch Elm disease, etc.
IV. Fungi
C. Ascomycetes
- life cycle
IV. Fungi
D. Basidiomycetes
- bear puffballs or mushrooms
as fruiting bodies
IV. Fungi
D. Basidiomycetes
- bear puffballs or mushrooms
as fruiting bodies
- haploid hyphae fuse in
dikaryotic hyphae.
IV. Fungi
D. Basidiomycetes
- bear puffballs or mushrooms
as fruiting bodies
- haploid hyphae fuse in
dikaryotic hyphae.
- these dikaryotic hyphae form
the fruiting structure.
IV. Fungi
D. Basidiomycetes
- bear puffballs or mushrooms
as fruiting bodies
- haploid hyphae fuse in
dikaryotic hyphae.
- these dikaryotic hyphae form
the fruiting structure.
- at the tip of each hyphae, the
basidium forms, in which
meiosis occurs to produce new
haploid spores.
- life cycle
Characteristics of Fungal Hyphae:
Septate versus Coenocytic
Mycelium: Large, Visible Mass of Hyphae
IMPORTANT DIVISIONS OF FUNGI
1. Deuteromycota
u
Not known to produce sexual spores.
u
Reproduce asexually.
u
Catch-all category for unclassified fungi:
– Pneumocystis carinii: Causes pneumonia in AIDS
patients. Leading cause of death in AIDS patients.
Originally classified as a protozoan.
– Candida albicans: Causes yeast infections of vagina in
women. Opportunistic infections of mucous
membranes in AIDS patients.
Opportunistic Infection by Candida
albicans in an AIDS Patient
Source: Atlas of Clinical Oral Pathology, 1999
Life Cycle of Eupenicillium (Ascomycete)
Reproduces Asexually and Sexually
Severe nail infection with Trichophyton rubrum in
a 37-year-old male AIDS patient.
Source: Intern. J. Dermatol. 31(1992): 453.
Disseminated Histoplasma capsulatum, skin infection.
Source: Microbiology Perspectives, 1999.
FUNGAL DISEASES
Mycosis: Any fungal disease. Tend to be chronic because fungi grow
slowly.
Mycoses are classified into the following categories:
I. Systemic mycoses: Fungal infections deep within the body. Can
affect a number if tissues and organs.
u
Usually caused by fungi that live in the soil and are inhaled. Not
contagious.
u
Examples:
– Histoplasmosis (Histoplasma capsulatum): Initial infection in
lungs. Later spreads through blood to most organs.
Systemic Mycosis: Histoplasmosis
Disseminated Histoplasma capsulatum, lung infection.
Source: Microbiology Perspectives, 1999.
FUNGAL DISEASES (Continued)
II. Cutaneous mycoses: Fungal infections of the skin, hair, and nails.
u
Secrete keratinase, an enzyme that degrades keratin.
u
Infection is transmitted by direct contact or contact with infected
hair (hair salon) or cells (nail files, shower floors).
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Examples:
– Ringworm (Tinea capitis and T. corporis)
– Athlete’s foot (Tinea pedis)
– Jock itch (Tinea cruris)
Cutaneous Mycosis
Ringworm skin infection: Tinea corporis
Source: Microbiology Perspectives, 1999
Cutaneous Mycosis
Candida albicans infection of the nails.
Source: Microbiology Perspectives, 1999.
FUNGAL DISEASES (Continued)
III. Subcutaneous mycoses: Fungal infections beneath the skin.
u
Caused by saprophytic fungi that live in soil or on vegetation.
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Infection occurs by implantation of spores or mycelial fragments
into a skin wound.
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Can spread to lymph vessels.
IV. Superficial mycoses: Infections of hair shafts and superficial
epidermal cells. Prevalent in tropical climates.
FUNGAL DISEASES (Continued)
Opportunistic mycoses: Caused by organisms that are generally
harmless unless individual has weakened defenses:
– AIDS and cancer patients
– Individuals treated with broad spectrum antibiotics
– Very old or very young individuals (newborns).
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Examples:
– Aspergillosis: Inhalation of Aspergillus spores.
– Yeast Infections or Candidiasis: Caused mainly by Candida
albicans. Part of normal mouth, esophagus, and vaginal flora.
ECONOMIC IMPORTANCE OF FUNGI
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25-50% of harvested fruits and vegetables are damaged by fungi.
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Fungal infections of plants are commonly called rots, rusts, blights,
wilts, and smuts.
– Phytophthora infestans: Caused great potato famine in mid1800s. Over 1 million people died from starvation in Ireland.
Many immigrated to the U.S.
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Beneficial fungi:
– Candida oleophila: Prevents fungal growth on harvested fruits.
– Saccharomyces cerevisiae: Used to make bread and wine.
– Genetically engineered yeast strains are used to make proteins
(Hepatitis B vaccine).
– Taxomyces: Produces anticancer drug taxol.
– Trichoderma: Produces cellulase. Used to make fruit juice.