630 Microbiology for Teachers

Fungal Diversity

Chytridiomycota - Chytridiomycetes or Chytrids

• morphology - globe-shaped cells with rhizoids
• reproduction
  • sexual - at maturity, the globe-shaped cells become sporangia which release motile spores; diploid zygote develops into new globe-shaped cell
  • asexual - mitosis
• habitat/importance
  • saprophytic decomposers which grow in on decaying plants or animals, mainly in freshwater habitats (including mud)
  • parasitic - some infect living plants, animals and other fungi

Oomycota - Oomycetes or "egg" fungi or water molds (distantly related to red algae)

• morphology - finely branched hyphal filaments, with cellulose (not chitin) cell walls
• reproduction
  • sexual - egg cell fertilized by sperm cell (or antheridium), diploid zygote develops into hyphae
  • asexual - motile (flagellated), diploid zoospores which develop into new hyphae
• habitat/importance
  • saprophytic - Saprolegna and Achyla are aquatic decomposers which grow as cottony masses on dead algae or small animals, mainly in freshwater habitats
  • parasitic - tobacco "blue mold" (Peronospora hyoscyami); late blight of potatoes (Phytophthora infestans); grape downy mildew (Plasmopara viticola); fish gills

Zygomycota - Zygomycetes, zygosporangium-forming fungi (~600 species)

• morphology - mycelial
• reproduction
  • sexual reproduction via zygospores - very resistant to harsh conditions
  • asexual spores (sporangiospores) formed in sporangia at tips of aerial hyphae
• habitat/importance
  • generally saprophytic decomposers in soil, important in plant decay
  • Rhizopus stolonifer (common bread mold) is used commercially to produce tempeh (from tofu), pharmaceuticals including anaesthetics, contraceptives, industrial alcohols, meat tenderizer, yellow dye for margarine

Ascomycota - Ascomycetes, sac fungi (~35,000 species)

• morphology - dimorphic (yeast or mycelium with septate hyphae)
• reproduction
  • sexual spores are ascospores - formed in ascus (= sac)
  • asexual spores are conidiospores
• habitat/importance - generally saprophytic decomposers in soil, but some are used for food and some are parasitic
  • helpful - Morchella esculenta (morels) and Tuber brumale (truffles) are edible; Saccharomyces (cerevisiae, carlsbergensis, ellipsoideus) used to make bread, beer, wine; Neurospora crassa genetics research tool (spoilage-inducing bread mold)
  • damaging (parasites, etc.) - Claviceps purpurea produces LSD, causes ergot of rye; Ophiostoma ulmi causes Dutch elm disease; Cryphonectria parasitica causes chestnut blight; Monilinia fruticola causes brown rot of stone fruits

Basidiomycota - Basidiomycetes, club fungi (~30,000 species)

• morphology - dimorphic (yeast or mycelium with septate hyphae and fruiting bodies we recognize as mushrooms, shelf fungi, puffballs, etc.)
• reproduction
  • sexual spores are basidiospores - formed by the basidium (club-shaped structure at tip of hyphae; may be inside a fruiting body called a basidiocarp)
  • asexual reproduction - budding, fragmentation of the mycelium, and by production of conidiospores, arthrospores, or oidia (Coprinus lagopus)
• habitat/importance - generally saprophytic decomposers in soil, but some are used for food and some are parasitic
  • helpful - Agaricus campestris bisporus is an edible mushroom
  • damaging (parasites, etc.) - Amanita phalloides is poisonous (produces phalloidin and alpha-amanitin); Cryptococcus neoformans, human pathogen; Puccinia graminis causes black stem wheat rust; Ustilago maydis - causes corn smut

Deuteromycota - Deuteromycetes or fungi imperfecti (~30,000 species)

• morphology - mycelial with septate (perforated), branched hyphae
• reproduction
  • sexual cycle not yet observed, hence fungi imperfecti; when sexual cycle is discovered, they are moved into one of the other three higher fungal divisions
  • asexual spores are conidiospores and are produced on conidiophores
• habitat/importance - generally saprophytic decomposers in soil, but some are used for food and some are parasitic
  • helpful - Penicillium chrysogenum, penicillin; Penicillium, cheese production (Gorgonzola, Camembert, Roquefort); Aspergillus, industrial acids, soy sauce
  • damaging - Microsporium, Trichophyton, Epidermophyton causes tineas; Candida albicans causes opportunistic infections; Histoplasma capsulatum causes histoplasmosis; Aspergillus flavus produces aflatoxin; Verticillium, plant wilt