Fungi

1
Fungi

• Chapter 30

2
Shared Characteristics

• Distinctive fungal features
• Fungi are heterotrophs.
• Fungi have several cell types.
• Some fungi have a dikaryon stage.
• Fungi have cell walls that include chitin.
• Fungi undergo nuclear mitosis.

3
The Body of a Fungus

• Fungi exist mainly in the form of slender
  filaments (hyphae).
• mycelium - mass of connected hyphae
• grows through and penetrates substrate

4
The Body of a Fungus

• Fungi cell walls are formed of polysaccharides
  and chitin.
• Mitosis is unique.
• nuclear envelope does not break down and re-form
  spindle apparatus formed within

5
How Fungi Reproduce

• Differ from most animals and plants in that each
  compartment of hypha can contain one,
  monokaryotic two dikaryotic or more nuclei
• Many nuclei intermingle in cytoplasm of fungal
  mycelium which can lack distinct cells
• heterokaryotic nuclei from genetically distinct
  individuals
• homokaryotic hyphae whose nuclei are
  genetically similar to one another

6
How Fungi Reproduce

• Fungi are capable of both sexual and asexual
  reproduction.
• Fungi reproduce sexually after two hyphae of
  opposite mating type fuse.
• in some fungi fusion two haploid cells
  immediately results in diploid cell (2n)

7
How Fungi Reproduce

• Spores most common means of reproduction
• may form from asexual or sexual processes
• most often dispersed by wind but some spread by
  insects or other small animals

8
How Fungi Obtain Nutrients

• All fungi obtain food by secreting digestive
  enzymes (exoenzymes)
• absorb the organic molecules produced (external
  digestion).
• hyphae network SA for absorption
• many fungi able to break down cellulose in wood

9

• Anaerobic fermentation provides flavor for wine
  and cheese.
• Fungi are decomposers
• Fungi often act as disease-causing organisms for
  both plants and animals.

10
Ecology of Fungi

• Mutualistic associations
• lichens - fungi and green algae
• mycorrhizae - fungi and plant roots

11
Four Major Groups of Fungi

• Four major groups
• Chytridiomycota
• Zygomycota
• Basidiomycota
• Ascomycota

12
Chytridiomycota

• aquatic, flagellated fungi
• most closely related to ancestral fungi

13
Zygomycota

• includes common bread molds
• hyphae produce clumps of erect stalks -
  sporangiophores form sporangia

14
Basidiomycota

• Most familiar fungi (mushrooms, toadstools,
  puffballs, rusts, and smuts)
• named for characteristic sexual reproductive
  structure, basidium

15
Ascomycota

• Very large group including yeasts, common molds,
  and morels
• Named for reproductive structure ascus

16
Ascomycota

• Yeasts
• unicellular - most reproduction is asexual and
  takes place by cell fission or budding
• ferment carbohydrates
• play a leading role in genetic research

17
Lichens

• Lichens are symbiotic associations between a
  fungus and a photosynthetic partner.
• fungal hyphae penetrate photosynthetic cells and
  transfer nutrients to fungal partner.

18
Mycorrhizae

• Roots of about 90 of all kinds of vascular
  plants are involved in mutualistic symbiotic
  relationships (mycorrhizae).

19
Mutualistic Animal Symbioses

• A range of mutualistic fungal-animal symbioses
  has been identified.
• ruminants
• leaf-cutter ants

20
Fungal Parasites and Pathogens

• Aflatoxins - carcinogenic compounds produced by
  strains of Aspergillus flavus
• grows on corn, peanuts, cotton seeds