Today:

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Today

• Review of the Fungus-like Protists
• The REAL Fungi

Reminder Fieldtrip Monday! Wear close-toed
shoes. Dress for the weather. Meet at the
Administration Building at 1 pm.
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The Absorptive Protists A Closer Look
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What do we know about these??
Could you draw a lifecycle??
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The Plasmodial Slime Mold Life Cycle
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The Dictyostelida- Cellular Slime Molds

• Feeding stage consists of solitary cells
  functioning individually
• When food is low, cells follow chemical trails to
  form an aggregate (pseudoplasmodium)
• Cells in the aggregate maintain their membranes
• Haploid organisms!
• Most have no flagellated stages

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The Dictyostelida- Cellular Slime Molds
http//dictybase.org/Multimedia/development/develo
pment.html
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The Oomycotes (Water Molds and Their Relatives)
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Oomycota Water Molds and Their Relatives

• Includes water molds, white rusts, and downy
  mildews
• All are heterotrophic stramenopiles (straw
  hair)
• May be unicellular or consist of multi-nucleated
  hyphae (convergent evolution!!)
• Have cell walls made of cellulose
• Most are diploid dominant (unlike true fungi!)
• Have biflagellated cells during their life cycle

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• White Rusts
• Generally parasites of terrestrial plants
• Flagellated zoospores infect and feed on plant
  tissues

white pine blister rust is the pale to orange
colored blisters formed on white pine stem after
infection
chrysanthemum with CWR
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Downy Mildews Also typically parasites of
terrestrial plants
Arabidopsis thaliana - Peronospora parasitica. P.
parasitica is a downy mildew pathogen belonging
to the oomycetes
Downey mildew on soybeans
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Other Famous Oomycetes

• Potato blight (caused Irish Famine- late 1840s)

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The Water Molds

• Important decomposers and parasites in aquatic
  systems

secondary Saprolegnia infection
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Next Thinking About Real Fungi
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General Characteristics
??
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General Characteristics

• Mostly multicellular eukaryotes
• More closely related to animals than plants!
• Distinguished by their
• Nutritional Mode
• Structural Organization
• Growth
• Reproduction

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Nutritional Mode- Fungi

• Heterotrophs
• Acquire nutrients by absorption
• External digestion (exoenzymes)
• Makes them important decomposers!
• Parasitic fungi digest and absorb tissues of host!

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Fairy Rings
Could you draw a typical fungal body?? Try to
include the following key terms hyphae, septa,
mycellium

• WHY??

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Structural Organization- Fungi

• Vegetative bodies usually diffusely organized
  within and around the food source
• Except yeasts, fungi constructed of filamentous
  hyphae
• Hyphae form an interwoven mat, a mycellium
• Largest mycellium discovered is 3.4 miles in
  diameter!!

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The Fungi Structural Organization
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Structural Organization- Fungi

• Most hyphae are divided into cells by cross-walls
  called septa (septa have large pores!)
• Some fungi are aseptate- no divisions within the
  hyphae. These are the Coenocytic Fungi
• Parasitic fungi have modified hyphae, haustoria,
  specialized to penetrate the tissues of the host
• Most fungal cell walls are composed of chitin

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Structural Organization- Fungi
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Fungal Growth

• Growth is extremely rapid! (can add 1 kilometer
  per day of hyphae!!)
• Possible because of efficient transfer of
  materials by cytoplasmic streaming to the tips

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Fungal Dispersal and Reproduction

• Fungi reproduce by releasing spores
• Spores may be produced either sexually or
  asexually
• A single fungus may produce trillions of spores

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Fungal Life Cycles

• Most fungal hyphae and spores are haploid
• Some mycelia may form through the fusion of two
  genetically distinct hyphae. This mycelium is
  then a heterokaryon.
• The distinct nuclei may remain isolated, or may
  mingle and even exchange chromosomes and genes
  via a cross-over like process.

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Sexual Reproduction in Fungi

• In sexually reproducing fungi, the union occurs
  in two stages
• 1. Plasmogamy- fusion of the parents
  cytoplasm
• 2. Karyogamy- fusion of haploid nuclei of
  the two parents
• During the time lag (minutes to centuries!) the
  mycelium is a heterokaryon
• Occasionally the haploid nuclei pair off, two to
  a cell. This mycelium is dikaryotic.

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Sexual Reproduction in Fungi
You Try!
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Fungal EvolutionAnimals and fungi from a common
aquatic, flagellated, protistan ancestor?
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Evolution of the Fungi
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The Chytridiomycota

• Mainly aquatic
• May be saprobes, parasites
• Form flagellated spores (zoospores) ? Protists??
• Most have coenocytic hyphae, some unicellular

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Chytrids and Fungal Evolution

• Chytrids are found associated with plants very
  early in the fossil record (408-360 million years
  ago)
• Molecular evidence also suggests these are the
  most primitive fungi

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The Zygomycota- the Zygote Fungi

• Mostly terrestrial in soil or on decaying
  material
• Distinguished by a resistant zygosporangium
• Hyphae are coenocytic with septa only where
  reproductive cells are formed

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You Try Modify your generic fungal lifecycle to
represent a zygomycete.
Zygomycete Life Cycle
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Famous Zygomycota

• The black bread mold, Rhizopus
• The dung fungus, Pilobolus

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The Glomero-mycetes

• Small but ecologically distinct group!
• Form arbuscular mychorrhizae

Photo Ryan Geil
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Evolution of the Fungi
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The Ascomycota (Sac Fungi)

• 30,000 species from marine, freshwater, and
  terrestrial habitats
• Unicellular yeasts to large elaborate morels!
• Many live with algae as lichens, may also form
  mycorrhizae with plants, or between cells in
  leaves!

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You Try Modify your generic fungal lifecycle to
represent an Ascomycete.
Ascomycetes
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Other Ascomycetes
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Infamous Ascomycetes
An American Chestnut Tree with Chestnut Blight
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The Basidiomycota- Club Fungi

• 30,000 fungi including mushrooms, shelf fungi,
  puffballs, and rusts smuts
• Important decomposers (lignin!), also form
  mycorrhiza

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You Try Modify your generic fungal lifecycle to
represent a Basidiomycete.
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Other Basidiomycetes
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Wood Rot

• Brown Wood Rot Fungi eats cellulose and leaves
  behind brown lignin
• White Wood Rot Fungi eats brown lignin and
  leaves behind white cellulose
• Very important to nutrient cycling!!

Images Tom Volks, University of Wisconsin
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Evolutionarily, the Fungi are Divided into Phyla
based on Reproductive Strategy
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Ecological Adaptations in the Fungi

• 1. Molds-
• Rapidly growing, asexually reproducing fungus
• Grow as saprobes or parasites on a variety of
  substrates
• Example Penicillium (an ascomycete)

• Molds that have no known sexual stage are called
  imperfect fungi (deuteromycetes)

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Ecological Adaptations in the Fungi

• 2. Yeasts-
• Unicellular fungi in moist of liquid habitats
• Reproduce asexually by simple division or budding
• Includes members of the Ascomycota, Basidiomycota
  and Imperfect Fungi.

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Ecological Adaptations in the Fungi

• 3. Lichens-
• Symbiotic association of millions of algae or
  cyanobacteria within a mesh of fungal hyphae
  (most commonly ascomycetes)

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Ecological Adaptations in the Fungi

• 3. Lichens-
• Lichens absorb most of their minerals from dust
  or rain, making them good colonizers, but
  sensitive to pollutants.
• Lichens survive in very arid conditions, but
  photosynthesize only when water levels are
  sufficient, resulting in extremely slow growth.

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Ecological Adaptations in the Fungi

• 4. Mycorrhizae-
• Mutualistic associations of plant roots and fungi
• Increase the absorptive surface of the plant
  roots
• Fungus provides minerals for organic nutrients
  synthesized by the plant
• Found in almost all vascular plants!

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Ecological Adaptations in the Fungi

• 4. Mycorrhizae-
• Can be endo or ecto-mycorrhizae
• Endomycorrhizae- penetrates the cortical cells
  (but not the cell membrane) usually a zygomycete
  (Arbuscular Mycorrhizal Fungi)
• Ectomycorrhizae- forms a sheath around the root
  usually a basidiomycete

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Ectomycorrhizae
Ectomycorrhizae occur in almost all tree species
in temperate and boreal forests. Short growing
seasons in these areas limit decomposition and
create nitrogen stress. The fungi release
peptidases (exoenzymes) that break down proteins,
releasing N-containing compounds.
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Endomycorrhizae
Endomycorrhizae are found in 80 of all plants,
especially in warm/tropical grasslands and
forests. They help supply phosphorus to the
plants.
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• Most vascular plants are associated with
  mycorrhizae.
• Photo Barley grown with (right) and without
  (left) mycorrhizae.

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An Unusual Niche Indian Pipe

• This plant does not photosynthesize!

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Other Interesting Fungi

• Some produce antibiotics, like penicillin!
• Discovered, accidentally, in 1928 (from
  Penicillium notatum)
• Tested in humans 1941
• Nobel prize, 1945- (Fleming, Florey, and Chain)

Photo Alexander Fleming's photo of the dish with
bacteria and Penicillin mold
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Other Interesting Fungi

• Food Production

SEM Saccharomyces cerevisiae
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Other Interesting Fungi

• Aflatoxins
• First identified from Aspergillus flavus when
  turkeys fed moldy peanut meal fell ill
• Many other mycotoxins now identified!

Aflatoxins appear to cause stunted growth, liver
problems and immune system suppresion, especially
in children Photo AgriForum
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Other Interesting Fungi

• Fungal Pathogens

Above Tinea dorporis (ring worm) - Acute -
Forearm At Right Top normal esophagus, Bottom
Esophageal candidiasis
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Fungal hyphae growing through a hair from a cat
with ringworm.
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Other Interesting Fungi

• Poisonous Mushrooms (Toadstools)
• Especially Amanita sp. (Deaths cap)
• Toxin produced inhibits mRNA synthesis!

Death Cap (Amanita phalloides) Photo
perspective.com
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Other Interesting Fungi

• Hallucinogenic mushrooms
• Produce two alkaloids, psylocibin and psylocin
  (structurally similar to serotonin and LSD)
• Resemble toxic mushrooms!!

Fly Agaric (Amanita muscaria) Photo
perspective.com
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Some Quick Lab Review
What is this? Can you identify key structures?
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Some Quick Lab Review
What is this? Can you identify key structures?
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Some Quick Lab Review
What is this? Can you identify key structures?
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Some Quick Lab Review
What is this? Can you identify key structures?