Fungi

1
Fungi

• gt100,000 sp. described, 1.5 mil. estimated
• everywhere land water
• important decomposers recycle ecosystem
  nutrients (incl. lignin!)
• pests
• decompose us our stuff
• cause 80 of plant diseases

2
fungal nutrition

• heterotrophs w/absorptive nutrition
• secrete enzymes, digest externally
• absorb through tips of filaments
• saprobes or parasites
• symbioses mycorrhizal fungi lichens

3
structure of fungi

• lots of surface area
• loose filamentshyphae
• mycelium all of the hyphae
• fruiting body sexual reproductive structure
  (made of filamentseg mushroom) Fig 31.2

4
structure of fungi

• hyphae coenocytic or septate (Fig 31.3)
• walls may have plasmodesmata or big pores
  (nucleus can go through)
• cell walls of chitinrequire N
• haustoria hyphae specialized for penetrating
  host (Fig 31.4)

5
fungal growth

• can be rapid and localized
• fairy ring mushrooms at edge of underground
  mycelium (see Fig 31.20)
• grass in center competes, grass at edge
  benefits

6
generalized life cycle fungi

• dispersed by spores
• mostly haploid life cycle
• unique to fungiheterokaryotic cells
• genetically diff nuclei (eg 2 of them)
• NOT diploid since nuclei not fused
• dikaryotic

7
generalized life cycle fungi

• mating strainschemically different
• syngamy (fertilization) in two steps
• 1) plasmogamycytoplasm fuses, produces
  heterokaryotic cell
• 2) karyogamynuclei fuse
• asexual lifecycleif conditions good (Fig 31.5)

8
yeasts

• unicellular, moist habitats
• cells divide asymmetrically (budding)
• CO2 for bread
• alcohol for wine, beer
• pink on shower curtains

9
molds

• rapid growth, asexual reprod.
• examples
• 1) bread mold (Zygomycete)
• 2) Penicillium (Ascomycete)
• blue mold on fruits used for cheese
• makes antibiotic penicillin

10
discovery of penicillin

• 1928 London (accident)
• not enough made
• USDA lab Peoria grow on corn waste
• worldwide search for best strain
• Peoria cantelope
• 1945 Nobel Prize (English team)

11
origin of fungi

• opisthokonts fungi animals protistan
  relatives
• flagella at posterior end of cell
• ancestors unicellular
• multicellularity evolved indply

12
Chytrids

• at base of fungal clade
• flagellate stage
• aquatic terrestrial
• unicells or (mostly) coenocytes
• saprobes or parasites
• symbionts

13
Zygomycetes

• resistant zygosporangium
• only heterokaryotic cell
• site of karyogamy meiosis
• rapid reproduction, mostly asexual
• coenocytic
• mostly saprobes

14
Zygomycete diversity

• 1) bread mold Rhizopus
• 2) dung fungus Pilobilus leans toward light
• sporangium shoots 50 km/hgt2m
• dunggtclean grassgtcowgtdung

15
Glomeromycete

• form arbuscular (endo) mycorrhizae
• tree-like branched hyphae (arbuscles)

16
Ascomycete asexual life cycle

• asexual spores (conidia) in chains
• mitosis, haploid

17
Example Aspergillus

• African spores infect Caribbean coral
• skin infections (burn victims)
• lungs (AIDS)
• aflatoxin (corn, peanuts)
• destroys liver
• protects plants
• makes citric acid

18
Ascomycete sexual life cycle

• fruiting body ascocarp
• (often cup shaped)
• hyphae haploid or dikaryotic
• sexual spores in sacs asci (sing. ascus)
• asci at tips of dikaryotic hyphae
• more extensive dikaryotic stage than zygomycota

19
Ascomycete sexual life cycle

• used for genetic studies

20
Ascomycota diversity

• 1) powdery mildew
• fuzzy grey mycelium on leaf
• spherical ascocarps
• cleistothecium closed cup

21
Ascomycota diversity

• 2) morels (Morchella)
• usually mycorrhizal
• assoc. w/oaks
• prized food for humans
• some false morels deadly poisonous

22
Ascomycota diversity

• 3) truffles
• spores dispersed via animals
• stinky chemical attractants
• underground ascocarps
• pigs and dogs

23
Ascomycota diversity

• 4) strangling fungus (Arthrobotrys anchonia,
  anchostrangle)
• captures nematodes
• chemical attractant, lassos