Fungi

1
Fungi

• General Characteristics
• Classification
• Symbiotic Relationships in Lichens

2
General Characteristics

• Eukaryotic
• Nonphotosynthetic
• Most are multicellular heterotrophs
• Most are microscopic molds or yeasts
• Have filaments called hyphae
• Cell walls contain chitin (also found in
  insects) distinguishes them from plants (cell
  walls of cellulose)

• Microscopic to 861,000 ft2
• Study of fungi mycology
• Feeding secrete enzymes then absorb digested
  nutrients through cell wall
• Store energy as glycogen
• Most are saprophytic (recyclers!)

3
Most fungi are

• Molds
• Tangled masses of filaments of cells
• Ex. Fungus that grows on bread and oranges

• Yeasts
• Unicellular organisms
• Colonies resemble those of bacteria
• Best known as microorganisms that make bread rise

4
Structure of Fungi
Mycelia
Rhizoids
5
Structure (cont.)

• Hyphae form mat called mycelium (see next slide)
• Divided hyphae called septate hyphae
• Non-septate hyphae are called coenocytic hyphae
• Hyphae grow by cell division at the tip,
  increasing mycelium
• Some can change form due to changes in
  environment (see Histoplasma capsulatum, page 544
  changes from mycelium to unicellular yeast due
  to temperature/nutrient availability in human)

6
Mat of hyphae mycelium
7
Histoplasma capsulatum

• Able to change form in response to changes in
  environment
• Grows as mycelium on ground
• Invades human increase in temperature
  available nutrients cause
• it to grow unicellularly

8
Reproduction
-most reproduce both sexually and asexually

• Asexual
• Fragmentation
• Septate hypha dries and shatters releases
  individual cells that act as spores
• Budding
• pinches off to produce a small offspring cell
• Sporangiophores
• Hyphae look like stalks
• Top has enclosing sac filled with sporangiospores
• Conidiophores
• No enclosing sac around conidia

9
Reproduction (cont.)

• Sexual
• Neither male nor female, but or -
• When and - of same species encounter,
  hyphae fuse then give rise to structure that
  produces and scatters genetically diverse spores
• Most are haploid throughout most of their life
  cycle

10
Phylum Zygomycota

• Most are terrestrial organisms
• Hyphae are coenocytic
• Rhizopus stolonifer
• Hyphae anchor mold to surface
• Hyphae that penetrate surface are called Rhizoids
• Hyphae that grow across the surface of bread are
  called Stolons
• Reproduction
• Congugation 2 compatible mating types meet
  hyphae via gametangium
• Gametantium from both hyphae contain nucleus from
  mating type
• Gametangia fuse
• Nuclei mix and fuse in pairs
• Now Zygosporangium
• Becomes dormant
• Good conditions
• sproangiophore
• grows, producing
• sporangium ruptures
• and releases haploid
• spores

11
Phylum Basidiomycota

• Club Fungi
• Form basidiaclublike reproductive structures
  during sexual reproduction (see ?)
• Basidiocarp
• Spore-bearing
• Mushrooms stalk cap
• Underside of cap gills lined with dikaryotic (2
  nuclei) basidia.
• Nuclei fuse to form zygote (2n) zygote undergoes
  meiosis4 haploid
• 4 basidiospores, released into air good
  conditionsthey germinate
• and form mycelia that grow underground if
  compatible mating types
• meet, their haploid hyphae fuse and form a
  basidiocarp which
• 
  appears above ground

12
Phylum Ascomycota

• Have saclike compartments where sexually
• produced spores form
• Sac Fungi
• Live parasitically
• Habitats include salt water, fresh water, and
  land
• Reproduction
• Hyphae of 2 types form male and female haploid
  gametangia
• Maleantheridium femaleascogonium
• Gametangia unite via a tube nuclei from male
  move to female dikaryotic hyphae
• grow out of the female and intertwine with the
  original (parent) monokaryotic
• hyphae, forming ascocarp cells are monokaryotic
• Ascocarp sacs called asci
• Saccharomyces cerevisiae
• (traditional brewers
• and bakers yeast)
• Make bread rise,
• ferments grapes,
• makes beer

13
Fungi imperfecti

• Fungi that do not have a sexual stage
• deuteromycota
• Most of the species of fungi that were formerly
  classified in this group, are now classified in
  the phylum Ascomycota
  

14
Mycorrhizae and Lichens

• Compare and contrast (using page 549)
• - Make sure to identify the 3 types of lichens
• - Make sure to know which phyla form mycorrhizae
  and to which lichens belong