Introduction to Mycology

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Questions and Answers

What is the primary study focus of mycology?

Study of viruses

Study of fungi (correct)

Study of plants

Study of bacteria

Which component is found in the cell walls of fungi?

Cell membrane

Peptidoglycan

Cellulose

Chitin (correct)

What type of organism is a saprophytic fungus?

Causes disease

Feeds on dead organic material (correct)

Feeds on living organisms

Forms symbiotic relationships

Which type of fungi forms a relationship where both organisms benefit?

Symbiotic Signup and view all the answers

What describes parasitic fungi?

Attacking living organisms and causing harm Signup and view all the answers

Which of the following statements about fungi is true?

Fungi can reproduce both sexually and asexually Signup and view all the answers

What role do mycorrhizae fungi play for plants?

Acting as a virtual root system to enhance nutrient absorption Signup and view all the answers

Which of the following best describes eukaryotic organisms?

Organisms with complex cells containing nuclei Signup and view all the answers

What shape do unicellular yeasts typically take?

Oval or circular Signup and view all the answers

Fungi are generally categorized as which type of organism?

Heterotrophs Signup and view all the answers

At what temperature does yeast typically thrive?

Near body temperature Signup and view all the answers

Which of the following statements about molds is true?

They are filamentous and multicellular. Signup and view all the answers

What is meant by dimorphism in fungi?

Fungi that can exist as both yeast and mold Signup and view all the answers

What type of fungi typically reproduce asexually through spores?

Molds Signup and view all the answers

What is the optimum pH range for fungal growth?

4-6 Signup and view all the answers

What type of fungi are molds classified as?

Aerobic Signup and view all the answers

What is a potential harmful effect caused by some mold spores?

Allergic rhinitis Signup and view all the answers

What temperature range is optimal for the growth of saprophytic molds?

20-30°C Signup and view all the answers

Which of the following statements about fungi's nutrient requirements is correct?

Fungi require less nitrogen and moisture than bacteria Signup and view all the answers

What is a disadvantage of using Lactophenol Cotton Blue?

It can have poor contrast. Signup and view all the answers

What is the primary function of Wood’s lamp in the fluorescence test?

To emit UV light for skin examination. Signup and view all the answers

Why is low pH beneficial in Sabouraud Dextrose Agar?

It inhibits growth of bacteria. Signup and view all the answers

What is the composition of Potato Dextrose Agar primarily intended to do?

Encourage fungal growth. Signup and view all the answers

Which antimicrobial agent in Mycosel inhibits saprophytic fungi?

Cyclohexamide. Signup and view all the answers

What environment is Brain Heart Infusion Media recommended for?

Yeast phase of dimorphic fungi at 35-37 degrees Celsius. Signup and view all the answers

How do yeast cells typically reproduce?

By binary fission and budding. Signup and view all the answers

What is the role of lactic acid in Lactophenol Cotton Blue?

It preserves fungal structures. Signup and view all the answers

What is a possible disadvantage of Sabouraud Dextrose Agar?

It may not support all fungal phases. Signup and view all the answers

What is a characteristic feature of the nuclei inside fungal hyphae?

They are haploid unlike plant cells. Signup and view all the answers

What process describes the production of sexual spores in molds?

Sexual reproduction Signup and view all the answers

Which type of spore is produced specifically by Candida species under adverse conditions?

Chlamydospores Signup and view all the answers

What type of asexual reproduction occurs through the fragmentation of hyphae?

Asexual spores Signup and view all the answers

What are hyphal cells in Candida albicans speculated to contribute to?

Colonization of organs Signup and view all the answers

Which of the following types of asexual spores are produced as compartments in hyphae?

Arthrospores Signup and view all the answers

What type of fungi are dermatophytes known to invade?

Skin, hair, and nails Signup and view all the answers

Which type of conidia is characterized as larger and septated, often spindle-shaped?

Macroconidia Signup and view all the answers

Which genus of dermatophytes is known for producing club-shaped macroconidia only?

Epidermophyton Signup and view all the answers

What is the function of pseudohyphae in Candida albicans?

Virulence factor Signup and view all the answers

What medium is utilized for the recovery of dermatophytes from hair, skin, and nails?

Dermatophyte Test Medium Signup and view all the answers

Which condition promotes the yeast-to-mold transition in Candida albicans?

Low nutrient levels Signup and view all the answers

What type of filaments are formed by Rhizopus during asexual reproduction?

Coenocytic hyphae Signup and view all the answers

What do blastoconidia represent in fungal reproduction?

Asexual spores formed directly from hyphae Signup and view all the answers

During the sexual reproduction of fungi, what is the first phase called?

Plasmogamy Signup and view all the answers

Which of the following spores is typically smaller than macroconidia?

Microconidia Signup and view all the answers

Which type of spores are produced by Ascomycetes during asexual reproduction?

Conidiospores Signup and view all the answers

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.
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.