Lecture 12 - Fungal Diversity Notes

Lecture Details

  • Course: Evolutionary Genomics of Fungi
  • Instructor: Prof. Yan Wang, Department of Biological Sciences, UTSC

Lecture Topics

  • Module Overview:
    1. Introduction & Road Map of the Course (Module 3) - Textbook: Chapter 1.3
    2. Cell Structure and Components - Textbook: Chapter 3
    3. Metabolism and Energy - Textbook: Chapter 6.1, 6.2, 6.3
    4. Chemical Reactions and Enzymes - Textbook: Chapter 6.4 & 6.5
    5. Cellular Respiration I - Textbook: Chapter 7.1-7.5
    6. Cellular Respiration II - Textbook: Chapter 7.6 & 7.7
    7. Photosynthesis I - Textbook: Chapter 8.1, 8.2, 8.3
    8. Photosynthesis II - Textbook: Chapter 8.4 & 8.5
    9. Cell Cycle and Cell Division - Textbook: Chapter 11.1, 11.4 & Chapter 14.1
    10. Regulation of the Cell Cycle and Cancer - Textbook: Chapter 11.5 & Chapter 14.2
    11. Tree of Life: Fungal Cells - Textbook: Chapter 32.1 & 32.2
    12. Tree of Life: Fungal Diversity - Textbook: Chapter 32.3

Core Concept

  • Fungal Diversity:
    • Fungi are the second most diverse group of eukaryotic organisms, next to animals.

Study on Fungal Diversity

  • American Journal of Botany:
    • Publication: 2011, Vol 98(3): 426-438
    • Estimated fungi on Earth: Approximately 1.5 million in 1991, with only 70,000 described. Current estimates suggest 5.1 million species based on high-throughput sequencing methods.
  • Importance of Fungi:
    • Major decomposers in many ecosystems.
    • Essential partners for various organisms, contributing enzymes and drugs, and serving as experimental organisms.

Diversity Types in Fungi

  • Types:
    • Saprotrophic Fungi
    • Endophytes
    • Plant-pathogenic Fungi
    • Human-associated Fungi
    • Aquatic Fungi
    • Mycorrhizal Fungi

Fungal Phylogeny

  • Major Groups:
    • Chytridiomycota: ~1000 species, characterized by a simple cellular structure not forming a true mycelium.
    • Zygomycetes: includes classes like Zoopagomycota and Mucoromycota; primarily parasites and pathogens or decomposers.
    • Glomeromycetes: mainly form mycorrhizal associations with plant roots, vital for plant nutrient absorption.
    • Basidiomycetes: ~25,000 species, known for complex multicellular fruiting bodies.
    • Ascomycetes: ~48,000 species, distinguished by asci containing spores arising after meiosis and mitosis.

Key Features of Dikarya

  • Contains two major groups: Ascomycetes and Basidiomycetes.
  • A defining feature is that every mitotic division results in the formation of new septa, controlling the number of nuclei per cell.
  • Meiosis followed by mitosis in Ascomycetes produces eight haploid spores, while Basidiomycetes have specialized cells called basidia for nuclear fusion.

Fungal Life Cycle

  • Basidiomycetes:

    • Fruiting bodies consist of dikaryotic hyphae.
    • Meiosis produces haploid spores which germinate to form haploid mycelia.

  • Chemical Interactions:

    • Fungi can manipulate host organisms, e.g., certain fungi infecting ants can alter their behavior to ensure spore dispersal.

Practical Implications

  • Fungal species, especially those forming mycorrhizal relationships, play significant roles in ecosystem functioning by enhancing plant nutrient uptake, influencing soil ecology, and providing food sources for various organisms.

Closing Notes

  • Exam preparations for Module 3 require focus on content related to fungal cell structures and diversity, metabolism, photosynthesis, and the cell cycle.
  • Test scheduled for Thursday, December 11th, 2025, with resources available on Quercus for review.
  • Feedback for course improvements is welcomed through the provided anonymous form.