Fungi Flashcards
Fungi characteristics
Q
- Eukaryotic, aerobic, unicellular or filamentous, heterotrophic, and encased in rigid cell wall.
- Reproduce via sexual or asexual means
- It also has a cell membrane inside the cell wall which contains ergosterol.
Why are fungi not like bacteria?
has membrane bound organelles
Why are fungi not like plants?
lack chlorophyll and are not photosynthetic
Why are fungi not like animals?
It has a cell wall! (made of chitin and cellulose)
Describe three means for categorizing fungi. Can they be subclassified?
- Linnean
- Functional Superficial fungal infections
- Functional Deep fungal infections
Yes - Fungal species may be subclassified as saprobes, symbionts, commensals or parasites
Examples of fungi that cause Superficial fungal infections and what they utilize for growth
DERMATOPHYTES
• Hyphal fungi utilizes keratin as a substrate for growth
CANDIDA
• Yeast that prefers glucose of interstitial fluids
PITYROSPORUM
• Yeast that prefers breakdown products of sebum
Yeast vs Hyphae
differences between morph forms?
Yeast forms→ round and oval
Hyphal forms (mold) → filamentous growth form (plural = mycelium), often branched and grow by apical extension.
Do yeast or hypha have septa?
Hypha - but can be nonseptate as well
Yeast vs Hyphae
which one is unicellular?
Yeast - unicellular
Hyphae - multicellular
Yeast vs Hyphae
Reproduction?
Yeast - reproduce by budding or fission
Hyphae - reproduce by formation of spores or conida (looks like a rake)
Two types of spores produced by hyphae
Macroconidium (large multinucleated spore)
Microconidium (small unicellular spore)
Rhizoids
specialized forms of hyphal elements that grow like roots from larger hyphae
Pseudohyphae
elongated yeast linked together like sausages, and do not have cytoplasmic connections between the compartments.
Which species of fungi are dimorphic and exist in yeast or hyphae?
o Some Can Have Both Phases = (For thermal dimorphic species)
- Sporothrix schenkii
- Coccidioides immitis
- Histoplasmosa capsulatum
- Blastomyces dermatitides
- Paracoccidiodes brasiliensis
morphology of the basic forms of asexual spores.
- CONIDIA
- SPORANGIA
- CHLAMYDOSPORES
- ARTHROSPORES
- SPHERULES
- BLASTOCONIDIA
Explain the morphology of the asexual spore:
CONIDIA
Born off of aerial hyphae (upward projecting hyphae) called conidophores.
May be macroconidium (large and multinucleated) or microconidia (small and unicellular).
Explain the morphology of the asexual spore:
SPORANGIA
Q
Similar to macroconidia, except spores are enclosed in membranous sac that can break from the sporangiophore (almost like a stalk) and release a sporangium.
Explain the morphology of the asexual spore:
CHLAMYDOSPORES
Thick walled round spores that are highly resistant to adverse environmental conditions. Terminal one can form at end of hyphae, or intercalary ones along and within hyphae.
Know it’s under stress if you see these.
Explain the morphology of the asexual spore:
ARTHROSPORES
Along hyphae, but numerous and elongated (shaped like barrel, ex. Coccidiodes immitis). Inhalation from environment can yield the disease.
Explain the morphology of the asexual spore:
SPHERULES
Large, typically in yeast form and filled with endospores
Explain the morphology of the asexual spore:
BLASTOCONIDIA
Yeasts that bud asymmetrically.
MOA of polyenes
“Polyenes punch holes”
○ Bind to ergosterol (fungicidal)
MOA of Azoles/Triazoles
○ Inhibit enzyme 14a-demethylase (enzyme that converts lanosterol to ergosterol); fungistatic.
○ Oral form also interferes with fungal CYP450
MOA of Allylamines/ Benzylamines (terbinafine)
○ Inhibit enzyme squalene epoxidase (required for ergosterol synthesis), and leads to accumulation of squalene within fungal cell (toxic!); fungicidal.
MOA of Echinocandins
Inhibit synthesis of glucan (in CW of some fungi) by inhibition of 1,3-b glucan synthase.
MOA of Flucytosine
interrupts DNA synthesis; fungistatic
MOA of Griseofulvin
Disrupts mitotic spindle formation, used in children withtinea capitis b/c of safety record; fungistatic.
