Chapter 23

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Chapter 23 The Fungi

• Domain - Eukarya
• Kindom - Fungi

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Kingdom Fungi

• Mycology study of fungi mycofungus,
  -logystudy
• More than 100,000 known species
• Nutrition
• Heterotrophic by absorption following secretion
  of enzymes most saprotrophic
• Some parasitic on living tissues of plant/animal
• Some mutualists (symbionts) with plant roots
  and algae
• eukaryotic organisms
• both unicellular (yeasts) and but mostly
  multicellular (mushrooms) forms
• found in almost all habitats free-living and
  parasitic forms represented

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Fungal facts

• Fungi perform important roles along with bacteria
  as decomposers within various ecosystems they
  also cause a variety of plant and animal diseases
• Commercial value of fungi includes role in the
  production of various cheeses the role of yeast
  fermentation in wine-making, brewing, and baking
  and the production of antibiotics (penicillin).
  Many mushrooms and truffles are edible.

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Fungal Terminology

• hypha - a single filament making up the body of a
  fungus
• mycelium - the mass of filaments (hyphae) of
  which a fungus is composed mycelium is the
  thallus (body) of most fungi
• septa - divide fungal hyphae into "cells" septa
  contain pores that allow intercellular
  communication including transfer of cytoplasm,
  ribosomes, mitochondria, and nuclei septate
  hyphae
• cell walls - composed of chitin (polymer of
  glucose) lack chloroplasts energy reserve is
  glycogen
• coenocytic fungi - cells fuse in certain fungi
  forming a continuous stream of cytoplasm and
  filaments containing many nuclei nonseptate
  hyphae

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Hyphae of fungi
coenocytic
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Fungal facts

• Fungi secrete hydrolytic digestive enzymes and
  then acquire nutrients through absorption
• proteins and other compounds synthesized by the
  mycelium are transferred by cytoplasmic streaming
  to the tips of the hyphae
• a process that allows fungi to grow very rapidly

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Reproduction of fungi

• Fungi reproduce sexually or asexually spores may
  be produced sexually or asexually
• In general, fungal sexual reproduction involves
  the following
• haploid hyphae ? dikaryotic stage ? diploid
  zygote
• ?-------------?-------- meiosis----?--------
  ---?

spores
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Fungal sexual reproduction, continued

• During sexual reproduction, haploid hyphae from
  two different mating types ( and - ) fuse.
• If nuclei do not fuse immediately, the resulting
  hypha is dikaryotic (contains paired haploid
  nuclei, (n n).
• a. In some species, nuclei pair but do not fuse
  for days, months, or even years.
• b. The nuclei continue to divide in such a way
  that every cell has at least one of each type of
  nucleus.
• When the nuclei fuse, the resulting zygote
  undergoes meiotic cell division leading to spore
  formation.
• Fungal spores germinate directly into haploid
  hyphae without embryological development.

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Fungal Spore Formation

• Spores are an adaptation to life on land and
  ensure that the species will be dispersed to new
  locations.
• A spore is a reproductive cell that can grow
  directly into a new organism.
• Fungi produce spores both during sexual and
  asexual reproduction.
• Although nonmotile, the spores are readily
  dispersed by wind.

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Fungal asexual reproduction

• Asexual reproduction can occur by three
  mechanisms
• Production of spores by a single mycelium is
  the most common mechanism.
• Fragmentation is when a portion of a mycelium
  becomes separated and begins a life of its own.
• Budding is typical of yeasts a small cell
  forms and gets pinched off as it grows to full
  size.

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Survey of Major Fungal Phyla Phylum Zygomycota

• 1. Phylum Zygomycota the zygospore fungi - 600
  species group composed of coenocytic hyphae
  reproduction by sporangium produce spores
• Examples Rhizopus stolonifera the common
  black, bread mold
• Also the mycorrhizal fungi (mycorrhizae) which
  form mutualistic associations with the root
  systems of various plants and help the plant with
  the uptake of water and nutrients (greater
  absorptive surface area) fungus benefits by
  receiving carbohydrates from the plant.
• Over 95 of vascular plants have mycorrhizae
  some also belong to Ascomycota and Basidiomycota.
  

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Phylum Ascomycota

• 2. Phylum Ascomycota - 60,000 species consist of
  single cell (yeasts) to mycelium of septate
  hyphae called "sac fungi" because of
  spore-producing saclike asci (sexual
  reproduction). Usually asexual reproduction by
  producing spores called conidia.
• The truffle (Tuber sp.) lives in association with
  oak and beech tree roots (mycorrhizal
  association) it can be inoculated with the
  fungus
• a. yeasts - unicellular fungi capable of
  fermentation usually reproduce asexually by
  budding
• Saccharomyces cerevisiae - beer and wines
  (ethanol, CO2)bread rising (CO2)
• Candida albicans is the causative agent of
  human yeast infections and oral thrush

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Phylum Ascomycota

• b. molds helpful and harmful to humans
• Stachybotrys chartarum black mold sick
  building syndrome
• Aspergillus sp.- soy sauce by fermentation of
  soybeans A. flavus grows on grain seed and
  secretes carcinogenic toxin
• Talaromyces (formerly Penicillium) antibiotic
  penicillin
• Athlete's fungus, ringworm (Tinea)
• Fungal flu (Midwest) Histoplasma sp. grows in
  mold and yeast forms in soil, associated w/ bird
  droppings-immune system/systemic illness
• Ergot of rye - Claviceps purpurea, produces
  lysergic acid human disease ergotism
• Chestnut blight - has virtually eliminated
  American chestnuts
• Dutch elm disease - transmitted by bark beetles
• Powdery mildews and leaf curl fungi impact leaves

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Note Phylum Deuteromycota now in Ascomycota

• Phylum Deuteromycota - the "imperfect fungi" due
  to the absence of a sexual stage includes
  Penicillium important in antibiotic and cheese
  production and Tolypocladium the source of
  cyclosporine

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Phylum Ascomycota
Morels, Cup Fungi, and Flask Fungi (below,
left-to-right)
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Phylum Ascomycota

• c. lichens - mutualistic (more-or-less)
  associations of an algae (Cyanobacteria) and a
  fungus (usually an Ascomycota, some
  Basidiomycota)
• Three types of lichens are recognized.
• a. Compact crustose lichens are often seen on
  bare rocks or tree bark.
• b. Foliose lichens are leaflike.
• c. Fruticose lichens are shrublike.

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Lichen forms
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a fruticose lichen - shrublike

• Reindeer moss

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Crustose lichen -crusty
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Foliose lichen, this one on a tree twig -
leaflike
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Gray frosted rosette lichen (Physcia biziana)
orange sunburst lichenXanthoria) on bark at the
south rim of the Grand Canyon, Arizona (both
Ascomycota)
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Lichen ecology
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Phylum Basidiomycota

• 3. Phylum Basidiomycota - 25,000 species called
  "club fungi" due to the club-shaped basidium, a
  spore-producing structure found in this group -
  gives rise to basidiospores.
• mushroom (basidiocarp) tightly packed hyphae
  cap, gills, stalk, rhizoids (small branching
  hyphae)
• mushrooms and toadstools shelf fungi, puffballs,
  stinkhorns, birds nest fungi, jelly fungi
• many edible species including portabella and
  shitake are in this group.
• the plant parasites wheat rusts and corn smuts
• Smuts and rusts are club fungi that parasitize
  cereal crops (e.g., corn, wheat, oats, and rye)
• Dont form basidocarps, numerous spores resemble
  soot

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Club fungi
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Basidiomycota

• Hygrocybe coccinea, Scarlet Hood mushroom

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Basidiomycota
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Basidiomycota
Stropharia species from Washington State
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Shelf fungus
Lenzites betulina
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Toothed fungi
Hydnum repandum
toothed fungi
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Crust fungus
Phanerochaete chrysorhizon
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Coral fungi
Clavulinopsis corallinorosacea
Ramaria stricta
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Amanitas very poisonous
Amanita muscaria
Amanita pantherina var. pantherina