Fungi Lecture Review

Fungi Overview

  • Fungi play an essential role in ecosystems, particularly in nutrient cycling and decomposition.

Taxonomy of Fungi

  • Domains and Kingdoms:
    • Domain Bacteria
    • Kingdom Eubacteria
    • Domain Archaea
    • Kingdom Archaebacteria
    • Domain Eukarya
    • Kingdom Protista
    • Kingdom Plantae
    • Kingdom Fungi
      • Phylum Zygomycota
      • Phylum Basidiomycota
      • Phylum Ascomycota

Characteristics of Fungi

  • Eukaryotic and non-photosynthetic organisms.
  • Morphological Forms:
    • Molds: Filamentous fungi.
    • Yeasts: Unicellular and sometimes form colonies.
  • Mycology: The study of fungi.
    • Interacts with organic matter as saprophytes, recycling nutrients by absorbing from dead organisms.

Structure of Fungi

  • Composed of hyphae: filamentous structures that make up the mycelium.
  • Hyphae characteristics:
    • Cell walls made of chitin, not cellulose (unlike plants).

Growth and Feeding Mechanism

  • Mycelium Formation: Hyphae combine to form a net-like structure.
  • Growth is mainly through cell division at the tips of the hyphae.
  • Decomposition: Fungi secrete digestive enzymes to break down organic materials.

Dimorphism in Fungi

  • Dimorphic Fungi: Can switch between mycelial and yeast forms based on environmental conditions.

Reproduction in Fungi

  • Asexual Reproduction:

    • Via spores: haploid reproductive cells that develop into new hyphae.
    • Formation of sporangium on sporangiophores.
    • Fragmentation: Breakage of hyphae.
    • Budding: Formation of new cells from parent yeasts.

  • Sexual Reproduction:

    • Limited to some species.
    • Mating types designated as + or - (not male or female).
    • Fusion of hyphae from different types results in genetically diverse spores.

Phylum Zygomycota

  • Structure: Differentiated hyphae, including rhizoids (anchor) and stolons (lateral growth).
  • Conjugation: Sexual reproduction involving the formation of gametangia that merge to form a zygosporangium.

Phylum Basidiomycota

  • Known as club fungi.
  • Produce basidia for spore formation, typically form mushrooms.
  • Sexual reproduction occurs via basidiospores from basidiocarp (the mushroom).

Phylum Ascomycota

  • Known as sac fungi.
  • Male and female gametangia fuse, leading to formation of ascocarp containing ascospores.

Symbiotic Relationships

  • Mycorrhizae: Partnership between plant roots and fungi; plants provide sugars while fungi enhance nutrient uptake.
  • Lichens: Symbiotic relationship between fungi and photosynthesizers, usually cyanobacteria or algae.

Fungal Pathogens and Diseases

  • Some fungi are pathogenic and can attack living tissues.
  • Common diseases:
    • Athlete's foot: Itchy skin condition caused by Trichophyton or Epidermophyton.
    • Ringworm: Skin infection.
    • Candidiasis: Yeast infections caused by Candida species.
  • Allergies can also result from mold spores.

Benefits of Fungi

  • Antibiotics: Many antibiotics, like penicillin, are derived from fungi.
  • Yeasts are essential for food production (e.g., breads, beer).
  • Numerous fungal products are utilized in several industries, including food and pharmaceuticals.

Notable and Unusual Fungi

  • Ophiocordyceps: A fungus that takes control of ant behavior, effectively turning them into "zombies." This highlights the complex interactions between fungi and their hosts.