Notes on Fungi

Chapter 1: Introduction to Fungi

  • Overview: Today’s lecture focuses on fungi, following previous discussions about bacteria and algae.
  • Evolution and Phylogeny: Fungi are classified into four primary groups:
    • Chitrids
    • Zygote fungi
    • Sac fungi
    • Club fungi
  • Characteristics of Fungi:
    • Body forms can be unicellular or filamentous (tube-like strands called hyphae, singular: hypha).
    • Mycelium is the mass of hyphae; sclerotium is a hardened mycelium mass for overwintering.
    • Can be multicellular with structures such as mycelial cores, rhizomorphs, and fruit bodies (e.g., mushrooms).
  • Feeding Mechanism:
    • Fungi grow through substrates, absorbing dissolved nutrients through extracellular enzymes they excrete.
    • They require a substrate to grow, leading to a sedentary vegetative state.
  • Cell Structure:
    • Cell walls made of chitin or cellulose.
    • Food stored as lipids and glycogen.
  • General Characteristics:
    • Eukaryotic organisms (true nucleus and organelles).
    • Require water and oxygen and are not obligate anaerobes.
    • Thrive in diverse habitats with organic matter; estimates suggest 69,000 to 100,000 described species and possibly 1.5 million species total.

Chapter 2: Bodies of Fungi

  • Types of Fungi:
    • Saprophytes: Feed on dead tissues/organic waste (e.g., decomposing wood).
    • Symbionts: Engage in mutual relationships with other organisms.
    • Parasitic fungi: Feed on living tissues (pathogens causing diseases).
  • Nutritional Process:
    • Absorb nutrients through heterotrophic absorption from organic sources (e.g., decaying leaves).
    • Enzymes released by hyphal tips break down organic matter for nutrient uptake.
  • Hyphal Structure:
    • Hyphae are tubular, made of chitin with potential cross-walls, which can result in multinucleated cells.
    • Hyphae grow primarily at their tips. Mycelium forms extensive networks for feeding.
  • Modifications of Hyphae:
    • Septate Hyphae: Have walls between cells.
    • Syncytial Hyphae: Continuous without walls.
    • Modifications can include structures for trapping prey (e.g., nematodes).
  • Mycorrhizae: A type of mutualism where fungi aid in nutrient and water absorption of plants.
    • Types include Zygomycota (invade root cells) and Ascomycota/Basidiomycota (do not penetrate root cells).

Chapter 3: Penicillium Hyphae

  • Ecto-Mycorrhizae: Fungi attach to plant roots (e.g., Russula mushroom on Western Hemlock).
  • Lichens:
    • Mutualism between fungi and algae/cyanobacteria (fungi provide structure, algae synthesize food).
    • Types include:
    • Crustose: Flat with crispy plates.
    • Foliose: Leafy but not true leaves.
    • Fruticose: Highly branched, appearing like beards.
  • Environmental Indicators: Lichens act as biological monitors for pollution, with varying sensitivity to pollutants. Specific species can indicate air quality based on their ability to accumulate contaminants.

Chapter 4: The Simple Fungi

  • Phylogenetic Groups:
    • Chytridiomycota (Chytrids): Simple fungi with motile spores, living in aquatic habitats, primarily as decomposers and parasites.
    • Zygomycota (Zygote fungi): Characterized by rapid growth and asexual reproduction, with significant roles in decomposition and some mycorrhizal relationships.
    • Ascomycota (Sac fungi): Known for producing spores in ascus; important in decomposition and include yeast (e.g., Saccharomyces).
    • Basidiomycota (Club fungi): Produce spores in basidia, are typically long-lived, and play roles in wood decomposition and mycorrhizal relationships.
    • Deuteromycota (Imperfect fungi): Rarely reproduce sexually, often rely on asexual reproduction and vegetative growth.

Chapter 5: Conclusion

  • Yeast and Molds:

    • Yeasts are single-celled fungi found in moist environments (e.g., Saccharomyces, Candida).
    • Molds reproduce asexually and can spoil food or be beneficial in antibiotics production; Botrytis is an example.

  • Human Interaction with Fungi:

    • Beneficial Effects: Decomposition and nutrient cycling, drug production (e.g., penicillin from Penicillium).
    • Harmful Effects: Can lead to food spoilage, diseases in humans and animals, allergies from mold spores, and destruction of materials (food, cloth, wood).

  • Further Study: Remaining topics on viruses and pathogens will be discussed in future lectures. For questions or clarifications, students are encouraged to reach out in the group chat.