뒤로Chapter 12: The Eukaryotes – Fungi, Algae, Protozoa, and Helminths
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Fungi: General Characteristics
Introduction to Mycology
Mycology is the branch of microbiology that studies fungi, a diverse group of eukaryotic organisms. Fungi play essential roles in ecosystems as decomposers, pathogens, and sources of industrial products.
Mycology: The study of fungi.
Chemoheterotrophs: Fungi obtain energy and carbon by decomposing organic matter.
Most fungi are aerobic or facultative anaerobes.
Comparison of Fungi and Bacteria
Fungi and bacteria differ in cellular structure, metabolism, and reproduction. The following table summarizes key differences:
Feature | Fungi | Bacteria |
|---|---|---|
Cell Type | Eukaryotic | Prokaryotic |
Plasma Membrane | Sterols present | Sterols absent (except Mycoplasma) |
Cell Wall | Glucans, mannans, chitin (no peptidoglycan) | Peptidoglycan |
Reproduction | Sexual and asexual reproductive spores | Endospores (not for reproduction); some asexual reproductive spores |
Metabolism | Limited to heterotrophic; aerobic, facultatively anaerobic | Heterotrophic, autotrophic, aerobic, facultatively anaerobic, anaerobic |
Major Features of Fungi
Fungi are a highly diverse group with over 600,000 species. They are found in various environments and have unique nutritional and structural adaptations.
Most fungi are multicellular; yeasts are unicellular.
Fungi do not carry out photosynthesis.
They absorb nutrients from their environment.
Include both pathogens and saprobes (decomposers).
Nutritional Adaptations of Fungi
Environmental Tolerance
Fungi are adapted to survive in a wide range of environmental conditions, often more extreme than those tolerated by bacteria.
Grow better at pH 5 (more acidic than most bacteria).
Can grow in high sugar and salt concentrations; resistant to osmotic pressure.
Can grow in low moisture content.
Can metabolize complex carbohydrates.
Vegetative Structures of Fungi
Molds and Fleshy Fungi
The main body of a fungus is called the thallus, which consists of long filaments known as hyphae. A mass of hyphae forms a mycelium.
Vegetative hyphae: Obtain nutrients.
Aerial hyphae: Involved in reproduction.
Yeasts and Dimorphic Fungi
Yeasts are unicellular fungi that reproduce by budding or fission. Some fungi are dimorphic, meaning they can exist in both yeast-like and mold-like forms depending on environmental conditions.
Budding yeasts: Divide unevenly.
Fission yeasts: Divide evenly.
Dimorphic fungi: Yeastlike at 37°C and moldlike at 25°C; many pathogenic fungi are dimorphic.
Example: Candida albicans is a dimorphic fungus that can cause opportunistic infections in humans.
