Fungi

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Fungi

• Chapter 31

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Fungi
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Fungi
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Fungi
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Fungi

• Unicellular
• Most are multi-cellular
• Tropics to tundra
• Aquatics to terrestrial
• Airborne spores
• Yeast in breads and beer

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Fungi

• Break down organic materials
• Recycle nutrients
• Help roots of plants absorb nutrients
• Disease causing (plants and animals)
• Treatment difficult

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Fungi

• Phylogenetically fungi are more closely related
  to animals than plants
• Common characteristics
• 1. Heterotrophs
• Secrete hydrolytic enzymes (exoenzymes) into
  surroundings (fallen logs, corpses, or wastes)
• Absorb the nutrients(organic molecules)

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Fungi

• 2. Several cell types
• 3. Dikaryon stage
• 2 haploid cells coexist in a single cell
• 4. Cell walls include chitin
• cellulose with nitrogen

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Fungi

• 5. Nuclear mitosis
• Nuclear envelope does not break down
• Mitosis takes place in the nucleus
• Cytokinesis

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Body structure

• Hyphae
• Tiny filaments
• Composed of cytoplasm
• Surrounded by a plasma membrane cell wall
• Cell wall has chitin
• Septa
• Cross-walls that separate cells of hyphae

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Hyphae
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Fig. 31-3
Cell wall
Cell wall
Nuclei
Pore
Septum
Nuclei
(b) Coenocytic hypha
(a) Septate hypha
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Body structure

• Mycelium
• Mass of connected hyphae
• Surrounds infiltrates material
• Maximizes contact with organic material
• Grows rapidly
• Grows underground so not visible

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Reproduction

• Each cell can have one or more nuclei
• Monokaryotic
• One nuclei
• Dikaryotic
• Two haploid nuclei that function independently

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Reproduction

• Dikaryotic hyphae
• Heterokaryotic
• Nuclei that are from two genetically distinct
  individuals
• Homokaryotic
• Nuclei are genetically similar

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Reproduction

• Sexually
• Asexually
• Spores are produced either way
• Spread easily through the wind or on insects
• Suitable environment give rise to new fungal
  mycelium

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Reproduction

• Sexual reproduction
• 2 compatible mating types fuse
• Usually 2 haploid fuse to form diploid
• Some fungi remain 1n 1n and not 2n
• /- length of time

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Reproduction

• Plasmogamy
• Fusion of cytoplasm of mycelia
• Karyogamy
• Fusion of nuclei
• Zygotes
• Meiosis
• Spore formation

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Reproduction

• Asexually
• Molds
• Produce haploid spores by mitosis
• Yeasts
• Mitosis
• Buds

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Fig. 31-5-3
Key
Heterokaryotic stage
Haploid (n)
Heterokaryotic (unfused nuclei from different
parents)
PLASMOGAMY (fusion of cytoplasm)
Diploid (2n)
KARYOGAMY (fusion of nuclei)
Spore-producing structures
Zygote
SEXUAL REPRODUCTION
Spores
ASEXUAL REPRODUCTION
Mycelium
MEIOSIS
GERMINATION
GERMINATION
Spores
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Nutrients

• External digestion
• Digest wood (cellulose)
• Absorb the glucose
• Lignin (found in wood)
• Decomposer of living or dead organisms
• Yield carbon, nitrogen and phosphorus

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Nutrients

• Obtain nutrients from tiny roundworms called
  nematodes
• Paralyze
• Penetrate the body
• Absorbs the nutrients from the body
• Used as a source of nitrogen

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Metabolic pathways

• Anaerobic fermentation
• Wines and cheeses
• Soy sauce
• Antibiotics and steroids
• Yeasts (single cell fungi)
• Bioremediation
• Using organisms to break up a toxin

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Symbiosis

• Lichens
• Fungus photosynthetic partner (algae)
• Mutualism some are parasitic
• Hyphae penetrate cell walls of algae
• Obtain nutrients from the algae
• Protects the algae from too much sun

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Symbiosis

• Lichens first to invade a harsh environment
• Colored - pigments -protect the algae from the
  sun
• Pigments are used as natural dyes

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Lichen
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Mycorrhizae

• Association of tree (plant) roots with fungi
• Fungi function as an extension of the roots
• Plants absorb more nutrients, such as Zn, P, Cu
• Fungi gets organic materials from the plant

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Mycorrhizae

• 1. Arbuscular
• Fungal hyphae penetrate the trees roots
• Form coils around roots
• More common
• 2. Ectomycorrhizae
• Hyphae do not penetrate the roots
• Helps trees grow in infertile areas

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Endophytes

• Fungus lives inside the plant
• Intercellular spaces
• Help defend the plant against herbivores
• Symbiotic relationship between fungi and ruminant
  animals
• Fungi helps digest the cellulose

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Parasitic

• Mycosis
• Fungal infection
• Ringworm
• Athletes foot
• Candida albicans

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Parasitic

• Aspergillus
• Produces toxin harmful to humans.
• Pneumocystis
• Causes a rare pneumonia in AIDS patients
• Chytridomycosis
• Fungal infection that harms amphibians
• Other fungal infections harm plants
• Chestnut trees, corn

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Fungi

• Mycologists scientists that study fungus
• Five groups
• 1. Chytrids
• 2. Zygomycetes
• 3. Glomeromycetes
• 4. Ascomycetes
• 5. Basidiomycetes

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1. Chytridiomycota (chytrids)

• Aquatic fungi
• Flagellated spores called zoospores
• Diverged earliest
• Chitin in the cell walls

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2. Zygomycota

• Bread molds
• Molds that grow on fruit
• Zygosporangium
• Contains one or more diploid nuclei
• Forms a hard covering
• Once it reaches conditions for growth
• Undergoes meiosis then mitosis
• Releases spores

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Zygomycota
Key
Haploid (n)
Heterokaryotic (n n)
Diploid (2n)
PLASMOGAMY
Mating type ()
Gametangia with haploid nuclei
Mating type ()
100 µm
Young zygosporangium (heterokaryotic)
Rhizopus growing on bread
SEXUAL REPRODUCTION
Dispersal and germination
Zygosporangium
KARYOGAMY
Sporangia
Spores
Diploid nuclei
Sporangium
ASEXUAL REPRODUCTION
MEIOSIS
Dispersal and germination
Mycelium
50 µm
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BREAD MOLD
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Fig. 31-6
2.5 µm
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Glomeromycetes

• Arbuscular mycorrhizae
• Hyphae intermingle with plant roots
• Very few species

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Ascomycota

• Sac fungi
• Marine, freshwater and terrestrial
• Yeast
• Asci sac like structure containing sexual spores
• Ascocarps contain asci
• Fruiting bodies
• Microscopic or macroscopic

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Ascomycota
Conidia mating type ()
Key
Haploid spores (conidia)
Haploid (n)
Dikaryotic (n n)
Diploid (2n)
Dispersal
Germination
Mating type ()
ASEXUAL REPRODUCTION
Hypha
PLASMOGAMY
Ascus (dikaryotic)
Conidiophore
Dikaryotic hyphae
Mycelia
Mycelium
SEXUAL REPRODUCTION
Germination
KARYOGAMY
Dispersal
Diploid nucleus (zygote)
Eight ascospores
Asci
Ascocarp
Four haploid nuclei
MEIOSIS
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YEAST
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MORELS
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TRUFFLES
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Blasidiomycetes

• Mushrooms, shelf fungi, puff balls
• Blasidium (Latin means little pedestal)
• Long-lived dikaryotic mycelium
• Leads to more genetic re-combinations
• Blasidiocarps (mushroom)
• produced sexually
• Fruiting bodies
• Wood decomposers

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Blasidiomycetes
Dikaryotic mycelium
PLASMOGAMY
Haploid mycelia
Mating type ()
Mating type ()
Gills lined with basidia
Haploid mycelia
SEXUAL REPRODUCTION
Basidiocarp (nn)
Dispersal and germination
Basidiospores (n)
Basidium with four basidiospores
Basidia (nn)
Basidium
Basidium containing four haploid nuclei
KARYOGAMY
MEIOSIS
Key
Haploid (n)
Dikaryotic (n n)
Diploid nuclei
Diploid (2n)
Basidiospore
1 µm
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