KINGDOM FUNGI

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KINGDOM FUNGI
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Characteristics of Fungi

• This kingdom contains heterotrophic eukaryotic
  organisms that are saprobes, absorbing their food
  from decaying matter.
• Fungi are decomposers. They release digestive
  enzymes into their immediate environment. These
  enzymes break down the dead organic matter.
  Fungi then absorb the digested food through the
  cell wall.
• Slime moulds take up their food by simple
  endocytosis.

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• The bodies of most fungi consist of threadlike
  filaments called hyphae. As the hyphae grow, they
  branch, forming a tangled mass of filaments
  called a mycelium that is well adapted to absorb
  nourishment from its food source.
• Most hyphae have cell walls strengthened by a
  substance called chitin, (a long-chain polymer of
  beta-glucose that forms a hard, semi-transparent
  material).

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Reproduction

• Most species in this kingdom reproduce asexually
  and sexually by means of spores. Spores are
  single reproductive cells that have a haploid
  number (23) of chromosomes
• The 100,000 species of fungi are grouped into
  divisions based on their pattern of sexual
  reproduction. (Phyla are called divisions in
  Kingdom Fungi).
• Fungi with spores in a case like structure
  (sporangium), are placed in division Zygomycota.
  Fungi with spores in a saclike structure (ascus),
  are placed in division Ascomycota. Fungi with
  spores that form in a club like structure
  (basidium), are placed in division Basidiomycota.
  

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Case like Fungi (Division Zygomycota)

• Most fungi in this division are terrestrial
  saprobes. One common mould is bread mould, or
  Rhizopus.
• Its tangled mass of mycelium grows and produces
  several types of hyphae. These hyphae (rhizoids)
  extend into the food source like roots of a
  plant. They absorb water and sugar from the
  bread supporting further growth.
• After a few days of favourable growing conditions
  black case like structures (sporangia) grow at
  the tips of the hyphae. Each sporangium can
  produce thousands of spores which may be
  transmitted to other food sources through the air
  currents. (asexual reproduction). Under less
  favourable conditions, Rhizopus reproduces
  sexually through conjugation forming a zygospore
  which remains dormant until the growing
  conditions improve.

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Rhizopus aka Bread Mould
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Sac like Fungi (Division Ascomycota)

• Fungi in this division are characterized by their
  formation of a sac structure used in
  reproduction. They include the mildews, some
  moulds, and some yeasts.
• Sac fungi produce two kinds of spores. Spores
  produced as a result of sexual reproduction are
  called ascospores. They are produced in an ascus
  or sac. Spores produced asexually are called
  conidia.
• Examples Powdery mildews are parasitic ascocarps
  that infect cereal grains, lilacs, roses and
  other plants.
• A truffle is an ascomycete that forms fruiting
  bodies underground. They are considered a
  delicacy and sell for hundreds of dollars.

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• Yeasts are unicellular. Some are grouped with
  the ascomycetes because they form an ascus in one
  stage of their life cycle.
• Each yeast cell is oval and surrounded by a cell
  wall. The cytoplasm contains a large vacuole and
  a nucleus. Under ideal conditions yeasts
  reproduce very rapidly by budding. Under poor
  conditions, yeasts reproduce sexually forming
  ascospores.
• Yeasts can tolerate conditions lacking oxygen and
  carry out anaerobic respiration, or fermentation.
  In this process, sugar molecules are broken down
  by enzymes in the yeast cells, releasing energy,
  carbon dioxide and alcohol.
• Bakers yeast is added to dough and the carbon
  dioxide released causes the dough to rise. Wine
  makers use strains of yeasts that generate high
  volumes of alcohol.
• Some yeasts cause infections in the skin, lungs,
  and kidneys. Many are parasitic and cause
  disease.

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Sac like Fungi Division Ascomycota
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Club like Fungi (Division Basidiomycota)

• This division includes mushrooms, rusts, smuts,
  puffballs, bracket fungi and some yeasts.
• Many members of this division are saprobes and
  others are parasites.
• Under damp conditions in soil or in rotting wood,
  the mycelial mass of hyphae form knobs that
  absorb water and grow quite large. These knobs
  become spore bearing structures called fruiting
  bodies.
• The umbrella like cap of mushrooms contains gills
  that radiate out like spokes on a wheel. Each
  gill bears thousands of club like reproductive
  cells called basidia. Each basidium contains
  several thousand haploid spores that are wind
  blown to an alternate location. The mycelia from
  two different spores are able to fuse. (See
  lifecycle on the next slide).

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• Parasitic rusts and smuts make up another
  important group of fungi. These cause damage to
  grain crops such as corn, oats, wheat, rye and
  barley.
• Bracket fungi can exist as saprobes on the wood
  of dead trees, or as parasites on the wood of
  living trees.
• Puffballs are round or pear-shaped fungi. Often
  white and resembling mushrooms they release their
  spores only when the fruiting body dries up and
  splits open.

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Imperfect Fungi

• There are some species that have no known sexual
  phases and so cannot be classified into
  divisions.
• Many of these species cause diseases in plants
  and animals, including humans.
• In 1928 Sir Alexander Fleming observed a green
  mould Penicillium growing on a petri dish
  containing Staphylococcus bacteria. He later
  isolated a chemical substance produced by the
  fungus (Penicillin). This was the first
  antibiotic to come into medical use. This
  prevents the formation of cells walls or cell
  membranes in reproducing bacteria.
• The common mould Trichophyton rubrum causes a
  contagious fungal infection called athletes foot.

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Fungal Associations

• Certain fungi associate with other organisms for
  the mutual benefit of both partners.
• Lichens are symbiotic associations of a fungus
  with either an alga or a cyanobacterium. The alga
  provides nourishment to the fungus through
  photosynthesis. The fungus provides the alga
  with water, essential minerals, and protection
  from dryness in barren and rocky habitats.
• Other fungi associate with the roots of plants.
  These associations are known as mycorrhizae. The
  fungus mycelium forms a thick web over the
  surface of a plants roots. The fungal mycelium
  absorbs water and minerals from the soil, which
  it passes to the root. The plant provides the
  fungus with amino acids and sugars.
• Still other fungi associate with leaf-cutting
  ants. The ants provide food for the fungi until
  it grows large enough to serve as food for the
  ants.

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Lichens
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Lichen Ecology

• Lichens can grow in very inhospitable
  environments. (rocks, gravestones, sides and
  branches of trees etc.)
• Lichens are very sensitive to air pollution,
  especially sulfur and nitrogen, and so they are
  natural indicators of air quality.
• Grow extremely slowly, usually 1-2 mm per year.
• Lichen uses break down rocks into soil, food
  source for caribou/ deer in the tundra, natural
  dyes, tweed

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Fungi Pros

• Yeasts- baking and brewing
• Antibiotics and drugs (penicillin, cephalosporin)
• Many organic acids are commercially produced with
  fungi. Eg. Citric acid in Coke is produced by an
  Aspergillus.
• Steroids and hormones eg. The pill
• Certain stinky cheeses eg. Blue cheeses,
  roquefort and camembert.

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Fungi Cons

• Can cause human disease, either directly or
  through their toxins.
• Can cause diseases in plants and animals (crops,
  etc.)
• Cause rot and contamination of foods.
• Can destroy almost every kind of manufactured
  good, with the exception of plastics and some
  pesticides.

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Fungi Review Questions

• 1. In which division in the kingdom Fungi are
  mushrooms found?
• a) Zygomycota b) Ascomycota c) Basidiomycota
  d) Imperfect Fungi
• 2. What are some similarities and differences
  between fungi and plants?
• 3. Describe the roles of fungi as decomposers and
  as parasites. Give examples.
• 4. What are mycelia and hyphae?
• 5. What carbohydrate is in the cell wall of
  fungus?
• 6. a) What are the parts of a lichen? b) What
  does each contribute to the other?
• c) Why are lichens important?
• 7. Given your knowledge of fungi, what growth
  conditions might favor the fungus that causes
  athletes foot?
• 8. a) With which kind of organism are mycorrhizae
  associated?
• b) Why are they not considered parasites?
• c) What role is played by each member of the
  relationship?
• 9. The reproductive cells of fungi are called
  _____.
• 10. What is a saprobe?
• 11. Explain the difference between a saprobe and
  a parasite.
• 12. What characteristic of yeast makes it an
  unusual fungus?
• 13. Certain types of mushrooms grow only at the
  base of a particular species of tree. Explain.
• 14. What kind of fungus is used to make
  penicillin?
• 15 What advantage would a fungus that produces an
  antibiotic have over one that does not?