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Questions and Answers
What is the primary study focus of mycology?
What is the primary study focus of mycology?
Which component is found in the cell walls of fungi?
Which component is found in the cell walls of fungi?
What type of organism is a saprophytic fungus?
What type of organism is a saprophytic fungus?
Which type of fungi forms a relationship where both organisms benefit?
Which type of fungi forms a relationship where both organisms benefit?
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What describes parasitic fungi?
What describes parasitic fungi?
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Which of the following statements about fungi is true?
Which of the following statements about fungi is true?
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What role do mycorrhizae fungi play for plants?
What role do mycorrhizae fungi play for plants?
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Which of the following best describes eukaryotic organisms?
Which of the following best describes eukaryotic organisms?
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What shape do unicellular yeasts typically take?
What shape do unicellular yeasts typically take?
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Fungi are generally categorized as which type of organism?
Fungi are generally categorized as which type of organism?
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At what temperature does yeast typically thrive?
At what temperature does yeast typically thrive?
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Which of the following statements about molds is true?
Which of the following statements about molds is true?
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What is meant by dimorphism in fungi?
What is meant by dimorphism in fungi?
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What type of fungi typically reproduce asexually through spores?
What type of fungi typically reproduce asexually through spores?
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What is the optimum pH range for fungal growth?
What is the optimum pH range for fungal growth?
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What type of fungi are molds classified as?
What type of fungi are molds classified as?
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What is a potential harmful effect caused by some mold spores?
What is a potential harmful effect caused by some mold spores?
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What temperature range is optimal for the growth of saprophytic molds?
What temperature range is optimal for the growth of saprophytic molds?
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Which of the following statements about fungi's nutrient requirements is correct?
Which of the following statements about fungi's nutrient requirements is correct?
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What is a disadvantage of using Lactophenol Cotton Blue?
What is a disadvantage of using Lactophenol Cotton Blue?
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What is the primary function of Wood’s lamp in the fluorescence test?
What is the primary function of Wood’s lamp in the fluorescence test?
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Why is low pH beneficial in Sabouraud Dextrose Agar?
Why is low pH beneficial in Sabouraud Dextrose Agar?
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What is the composition of Potato Dextrose Agar primarily intended to do?
What is the composition of Potato Dextrose Agar primarily intended to do?
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Which antimicrobial agent in Mycosel inhibits saprophytic fungi?
Which antimicrobial agent in Mycosel inhibits saprophytic fungi?
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What environment is Brain Heart Infusion Media recommended for?
What environment is Brain Heart Infusion Media recommended for?
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How do yeast cells typically reproduce?
How do yeast cells typically reproduce?
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What is the role of lactic acid in Lactophenol Cotton Blue?
What is the role of lactic acid in Lactophenol Cotton Blue?
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What is a possible disadvantage of Sabouraud Dextrose Agar?
What is a possible disadvantage of Sabouraud Dextrose Agar?
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What is a characteristic feature of the nuclei inside fungal hyphae?
What is a characteristic feature of the nuclei inside fungal hyphae?
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What process describes the production of sexual spores in molds?
What process describes the production of sexual spores in molds?
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Which type of spore is produced specifically by Candida species under adverse conditions?
Which type of spore is produced specifically by Candida species under adverse conditions?
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What type of asexual reproduction occurs through the fragmentation of hyphae?
What type of asexual reproduction occurs through the fragmentation of hyphae?
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What are hyphal cells in Candida albicans speculated to contribute to?
What are hyphal cells in Candida albicans speculated to contribute to?
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Which of the following types of asexual spores are produced as compartments in hyphae?
Which of the following types of asexual spores are produced as compartments in hyphae?
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What type of fungi are dermatophytes known to invade?
What type of fungi are dermatophytes known to invade?
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Which type of conidia is characterized as larger and septated, often spindle-shaped?
Which type of conidia is characterized as larger and septated, often spindle-shaped?
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Which genus of dermatophytes is known for producing club-shaped macroconidia only?
Which genus of dermatophytes is known for producing club-shaped macroconidia only?
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What is the function of pseudohyphae in Candida albicans?
What is the function of pseudohyphae in Candida albicans?
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What medium is utilized for the recovery of dermatophytes from hair, skin, and nails?
What medium is utilized for the recovery of dermatophytes from hair, skin, and nails?
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Which condition promotes the yeast-to-mold transition in Candida albicans?
Which condition promotes the yeast-to-mold transition in Candida albicans?
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What type of filaments are formed by Rhizopus during asexual reproduction?
What type of filaments are formed by Rhizopus during asexual reproduction?
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What do blastoconidia represent in fungal reproduction?
What do blastoconidia represent in fungal reproduction?
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During the sexual reproduction of fungi, what is the first phase called?
During the sexual reproduction of fungi, what is the first phase called?
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Which of the following spores is typically smaller than macroconidia?
Which of the following spores is typically smaller than macroconidia?
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Which type of spores are produced by Ascomycetes during asexual reproduction?
Which type of spores are produced by Ascomycetes during asexual reproduction?
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Study Notes
Mycology
- The study of fungi, including their structure, biochemistry, impact on humans, and the diseases they cause.
Fungal Characteristics
- Eukaryotic organisms
- Cell walls contain chitin, unlike bacteria (peptidoglycan) and plants (cellulose).
- Can be single-celled (yeasts) or multicellular (molds).
- Reproduce sexually or asexually.
- Heterotrophic, meaning they obtain nutrients from other organisms.
Fungal Nutrition
- Saprophytic: Fungi that break down dead organic matter for food.
- Symbiotic: Fungi living in mutually beneficial relationships with other organisms.
- Parasitic: Fungi that live in or on other organisms and cause harm.
Mycorrhizae
- Symbiotic relationship between fungi and plant roots.
- Fungi help plants absorb water and nutrients from the soil.
- Plants provide fungi with essential nutrients.
Dimorphism
- Some fungi can exist as both yeast and mold forms depending on environmental conditions.
- Yeast form at 37°C (body temperature).
- Mold form at room temperature.
- Example: Sporothrix schenckii
Reproduction
-
Asexual:
- Spore release into the air.
- Fragmentation of hyphae.
-
Sexual:
- Production of sexual spores.
Fungal Cultures
-
Optimum Growth Temperatures:
- Saprophytes (molds): 20-30°C.
- Parasitic fungi (yeasts): 30-37°C.
- Standard Incubation Temperature: 30°C.
- pH: 4-6 (average 5.0).
- Osmotic Pressure: Fungi are more resistant than bacteria.
- Nutrition: Fungi require less nitrogen and moisture than bacteria.
-
Oxygen:
- Molds are aerobic.
- Yeasts are facultative anaerobes (can live with or without oxygen).
- Metabolism: Fungi can metabolize complex carbohydrates like lignin in wood.
Harmful Effects of Fungi
- Allergies: Mold spores can trigger allergic rhinitis.
- Mycoses: Direct fungal infections in animals (including humans).
Fungal Staining
- 10% Potassium Hydroxide: Used to clear skin and nail samples to visualize fungal elements.
-
Lactophenol Cotton Blue:
- Lactic acid preserves fungal structures.
- Phenol is a killing agent.
- Cotton blue stains fungal structures blue.
Fluorescence Test
-
Wood's lamp (UV light):
- Emitting wavelength 320-450 nm (peak 365 nm).
- Infected hair and skin may fluoresce when examined in the dark.
Culture Media
-
Sabouraud Dextrose Agar (SDA):
- Primary isolation media for most fungi.
- Low pH inhibits bacterial growth.
- Disadvantages: May not support growth of all yeast phases, high susceptibility to contamination.
-
Potato Dextrose Agar (PDA):
- Composed of potato infusion and dextrose, promoting fungal growth.
- Cheaper than SDA but less optimal.
-
Mycosel (SDA-CC):
- Contains antimicrobial supplements:
- Cycloheximide: Inhibits saprophytic fungi.
- Chloramphenicol: Inhibits Gram-bacterial growth.
- Can substitute Chloramphenicol with Gentamicin or Tetracycline.
- Contains antimicrobial supplements:
-
Brain Heart Infusion Media (BHI):
- Recommended for yeast phase of dimorphic fungi at 35-37°C.
- Made from pig heart and calf brain, enriched with nutrients to promote growth of fastidious fungi.
Fungal Reproduction: Asexual
-
Yeast:
- Binary fission.
- Budding.
- Pseudohyphae formation.
-
Molds:
- Fragmentation of Hyphae: Breaking off pieces of hyphae to form new fungi.
- Asexual Spores: Different types of spores produced by molds.
Fungal Spores: Asexual
-
Chlamydospore:
- Thick-walled, resistant spores formed by Candida species in adverse environments.
- Rounded, enlarged hyphal segments.
-
Blastospore/Blastoconidia:
- Budding yeast spores.
-
Arthrospore:
- Rectangular spores formed by fragmentation of hyphae.
- Found in Coccidioides immitis.
-
Macroconidia and Microconidia:
- Macroconidia: Large, multicellular, septated spores.
- Microconidia: Small, single-celled, round or oval spores.
-
Conidiospore:
- Spores produced in a chain at the tip of a conidiophore.
- Formed by phialides (flask-shaped projections).
-
Sporangiospore:
- Asexual spores contained within a sac-like structure called a sporangium.
- Found in nonseptated hyphae of Zygomycetes (e.g., Rhizopus, Mucor, Absidia).
Dermatophytes
- Fungi that require keratin for growth.
- Cause superficial infections of skin, hair, and nails.
-
Genera:
- Microsporum: Hair and skin only.
- Trichophyton: Hair, skin, and nails.
- Epidermophyton: Skin and nails only.
Dermatophyte Test Medium
- Used to recover dermatophytes from samples (hair, skin, nails).
- Detects the production of alkaline metabolites by dermatophytes, causing a color change in the medium.
Fungal Reproduction: Sexual
-
Three Phases:
- Plasmogamy: Fusion of haploid fungal cells, resulting in a dikaryotic cell with two nuclei.
- Karyogamy: Fusion of the two nuclei to form a diploid nucleus.
- Meiosis: Diploid nucleus undergoes meiosis to produce haploid nuclei and spores.
Fungal Sexual Spores
-
Ascospores:
- Produced in a sac-like structure called an ascus.
- Typically occur in clusters of four or eight.
-
Zygospores:
- Resulting from the fusion of two identical cells arising from fused hyphae.
-
Basidiospores:
- Contained in a club-shaped structure called a basidium.
- Commonly found in mushrooms.
Fungal Phyla
-
Ascomycetes:
- Reproduce sexually by forming ascospores.
- Reproduce asexually by forming conidiospores, microconidia, and macroconidia.
-
Zygomycota:
- Aseptate hyphae.
- Asexual spores: Sporangiospores.
- Sexual spores: Zygospores.
- Clinically important members: Rhizopus, Mucor, Absidia.
-
Basidiomycetes:
- Reproduce sexually by forming basidiospores.
- Reproduce asexually by hyphal fragmentation.
Imperfect Fungi (Deuteromycetes)
- Fungi that do not exhibit a sexual stage.
- Example: Penicillium.
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Description
Explore the fascinating world of mycology, the study of fungi. This quiz covers the characteristics, nutrition, and unique relationships fungi have with other organisms. Test your knowledge on key concepts such as mycorrhizae and fungal dimorphism.