Mycology - Introduction Flashcards
What are the key descriptors of a fungus?
- Eukaryotic
- Heterotrophic
- Devoid of chlorophyll
- Obtains nutrients by absorption
- Reproduces by spores
- Multicellular, except yeasts
- Contain cell walls
Define heterotroph.
A heterotroph is an organism that needs to feed on other organisms in order to make their own energy-containing organic molecules. Includes:
- Saprophytes
- Parasites
- Symbionts
Define saprophyte.
An organism that obtains food from decaying matter.
What is contained in the fungal cell wall?
- Chitin microfibrils (β(1-4)-linked polymer of N-acetylglucosamine)
- β-linked glucans
- Glycoprotein
What type of sterol is contained in the plasma membrane of fungi?
Ergosterol
What are the different morphologies of fungi?
- Moulds (Filamentous)
- Yeasts
- Yeast-like (yeasts producing pseudohyphae)
- Dimorphic
What are the characteristics of moulds?
- Filamentous
- Multicellular
- Generally found in nature
- Have hyphae
What are hyphae?
Cylindrcal, branching filaments composed of a tubular cell wall filled with cytoplasm and organelles. Usually 2-10 μm in diameter.
Can be non-septate coenocytic, or septate hypha.
What are the characteristics of yeasts?
- Mostly classified with Ascomycetes
- Generally spherical, oval, or cylindrical
- Common form found in tissue lesions
Under what conditions do dimorphic fungi change?
Found as moulds at lower temperatures/room temperature, and change to yeasts at body temperature (37ºC).
e.g. Histoplasma
How do filamentous fungi asexually reproduce?
Conidiophores on the ends of hyphae produce conidia (spores) that can germinate and become new hyphae.
How do yeasts asexually reproduce?
Budding
What are the four classifications (phylums) of fungi based on sexual reproduction?
- Chytridiomycota (flagellated, mostly aquatic)
- Zygomycota (Rhizopus decomposes strawberries)
- Ascomycota (yeasts, molds, morels, truffles)
- Basidiomycota (Cub-fungus)
- Deutromycetes (no known sexual spores)
What are the main steps of sexual reproduction of fungi?
- Two different mating types (+/-) come into contact (n)
- They undergo plasmogamy (n+n)
- Produces a dikaryotic/heterokaryotic hypha(e)/mycelium (n+n)
- They undergo karyogamy (n+n→2n)
- Meiosis to form haploid nuclei (n)
- Mitosis to form spores
- Dispersal
- Germination
What are the types of diseases that pathogenic fungi cause?
- Superficial (dead skin)
- Cutaneous (epidermis, hair, nails)
- Sucutaneous (dermis, subcutis)
- Systemic (internal organs)
- Opportunistic (internal organs)
