Mycology: Ascomycota and Notable Genera

Notable Genera

• Mucor and Rhizopus: Commonly found on food items such as bread and strawberries.

Ascomycota ("Sac Fungi")

• Sexual Reproduction: Occurs in sac-like structures known as asci.
• Asexual Reproduction: Frequently observed alongside sexual methods.
• Ecological Role: Acts as decomposers and pathogens, with many forming lichens.
• Notable Members: Includes cup fungi, morels, and truffles.
• Plant Parasites: Many species are significant plant pathogens.

Basidiomycota ("Club Fungi")

• Sexual Reproduction: Occurs in structures called basidia.
• Asexual Reproduction: Less common compared to Ascomycota.
• Long-lived Mycelia: Characterized by persistent dikaryotic mycelia (n+n).
• Ecological Role: Acts as important decomposers and plant parasites.
• Notable Members: Includes mushrooms, polypores, puffballs, rusts, and smuts.

Deuteromycota ("Imperfect Fungi")

• Characteristics: Fungi that rarely or never reproduce sexually.
• Reproduction: Primarily using asexual spores.

Specialized Fungal Relationships

• Mycorrhizae ("Fungus Roots"): Mutualistic relationships between fungi and plant roots.
  • Zygomycota: Hyphae invade root cells directly.
  • Ascomycota & Basidiomycota: Hyphae invade roots but do not penetrate cells.
  • Ecological Importance: Vital for nutrient and water uptake in plants.
• Lichens: Symbiotic relationship between a fungus and an alga or cyanobacterium.
  • Types:
    • Crustose: Crust-like, tightly bound to substrate.
    • Foliose: Leaf-like, flat sheets not tightly bound.
    • Fruticose: Finely branched, free-standing or hanging structures.

Characteristics of Fungi

• Eukaryotic Nature: Fungi consist of eukaryotic cells with a true nucleus and organelles.
• Cell Wall Composition: Made primarily of chitin and sometimes cellulose.
• Food Storage: Store nutrients as lipids and glycogen.
• Environmental Requirements: Need water and oxygen; can thrive in various habitats with organic matter.
• Diversity: Estimated between 69,000 and 100,000 described species, with potential total species around 1.5 million.

Body Structure

• Hyphae: Tubular structures forming the basic unit of fungi; multinucleate with walls of chitin.
  • Crosswalls (Septae): Can form compartments within hyphae.
• Mycelium: An aggregate of hyphae that constitutes the vegetative part of fungi.
• Sclerotium: A hardened mass of mycelium used for overwintering.
• Multicellular Forms: Include mycelial cords, rhizomorphs, and fruiting bodies like mushrooms.

Fungal Growth and Nutrition

• Heterotrophy: Fungi absorb nutrients from other organic sources.
  • Types of Heterotrophs:
    • Saprophytes/Saprobes: Decompose dead tissues or organic waste.
    • Symbionts: Form mutualistic relationships (e.g., mycorrhizae).
  • Pollution Indicators: Lichens are sensitive to air pollution, useful for environmental monitoring.

Human-Fungi Interactions

• Beneficial Effects:
  • Decomposition: Recycling of nutrients and carbon.
  • Biosynthesis: Production of drugs, antibiotics, alcohol, and fermented foods.
  • Model Organisms: Used for genetic and biochemical research.
• Harmful Effects:
  • Destruction: Damage to food, lumber, and textiles.
  • Diseases: Cause human and animal infections, including allergies.
  • Toxins: Production of harmful substances in food (e.g., aflatoxins).
  • Plant Diseases: Many fungi are key contributors to serious plant illnesses.

Fungal Life Cycles

• Chytridiomycota: Features motile spores that swim using flagella.
• Zygomycota: Formation of a zygospore after hyphal fusion from different mating types.
• Ascomycota: Production of ascospores within asci during sexual reproduction.
• Basidiomycota: Generation of basidiospores on club-shaped basidia structures.