Flashcards in 3.0 Fungi Deck (25)
Fungal cell wall is mainly composed of _______________
Glucan = polymer of ___________
Mannan = polymer of __________
Fungal cell wall is mainly composed of polysaccharides
Glucan = polymer of glucose
Mannan = polymer of mannose
Plasma membranes of fungi contain ________
Plasma membranes of fungi contain ergosterols
What is the structure of the fungal cell wall?
1) Inner chittin layer
Long straight chain
2) Outer glucan layer
3) Embedded glycopeptides
Asparagine - N-linked mannose/galactose
Serine/threonine - O-linked mannose/galactose
What is the structure of yeasts?
(candida can have pseudohyphae structure)
What two types of mitosis occurs in yeasts?
1) Symmetrical binary fission
2) Asymmetrical budding
What is the structure of filamentous moulds?
Hyphae (thin, branching cylinders)
Can be septate or aseptate
Mycelium = interwoven mass of hyphae
How does mitosis occur in hyphae?
-Mitosis only occurs at tips/side branches
What are dimorphic fungi?
22 degrees = filamentous morphology
37 degrees = Yeast
Brief overview of asexual reproduction:
Occurs most of the time
Spores produced by mitosis
Yeasts → internal spores
Moulds → external spores (condida) or internal spores (sporangium)
What fungal species only reproduces using asexual reproduction?
Brief overview of sexual reproduction:
Haploid fungus → sexual structures (motile gametes or sexual hyphae)
2 x sexual structures fuse → nuclei fuse → diploid → re-assortment and recombination
What are the three different types of sexual spores?
1) Ones that form internally within tubules (Ascus)
2) Ones that form externally on club like structures (Basidium
3) Ones that form from fusion of sexual hyphae
Complete the following statements regarding the nutrition of fungi:
• Fungi rely on preformed ______ compounds as sources of energy and carbon
• Secrete enzymes into the environment ⟶ ___________
• Absorb simple soluble molecules through ___________
• Yeasts live in _______ environments
• Hyphae __________ food material
• Fungi rely on preformed organic compounds as sources of energy and carbon
• Secrete enzymes into the environment ⟶ extracellular digestion of food material
• Absorb simple soluble molecules through channels in the fungal cell wall
• Yeasts live in moist environments
• Hyphae penetrate into food material
Fungi that feed on dead plant or animal material
Majority of fungi
What metabolites can fungi produce?
3) Antibiotics - Pencillin, cephalosporin, streptomycin
4) Immuno-suppressants - ciclosporin
5) Other drugs - ergometrine, ergotamine
6) Toxins - alphatoxins
What are lectins?
Proteins that have a specific carbohydrate recognition domain (many fungal PRRs are lectins)
List 6 fungal PAMPs and their PRRs:
1) Mannose-rich structures
- Mannose binding lectin (MBL) ← soluble
5) O-linked mannose
6) N-linked mannose
- Mannose receptor
What defects in host defences can lead to increased fungal infections?
1) Impaired fungal sensing (β-1,3-glucan)
- ↑ superficial infections
- Dextrin-1 deficiency
- CARD9 mutation
2) Impaired IL-17 immunity
- ↑ superficial infections
- IL-17 receptor deficiency
- Autoantibodies (anti IL-17/22)
3) Impaired neutrophils
- ↑ deep infections (Aspergillus)
4) Impaired T-cells/macrophages
- ↑ superficial + deep infections (Yeast + dimorphic)
What occurs following ingestion of the fungal toxin ergotamine?
It is a potent vasoconstrictor → ischamia and gangrene of digits
What is a common commensal fungus?
Candida albicans (throat, gut and vagina)
What is another name for superficial fungal infections?
Examples of superficial fungal infections:
1) Dermatophye moulds
- Spores transmitted by person-to-person contact / sharing clothing
- Chronic infection → toxins → Type IV hypersensitivity
2) Candida Albicans
- Chronic finger nail infection
3) Malassezia furfur
- causes pityriasis versicolor (blotchy skin rash - does not tan)
Example of subcut fungal infection:
Rose picker's disease (dimorphic sporothricx schenckii)
Examples of systemic pathogens: