Fungi: Molds and Cultures
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Questions and Answers

Which surface texture of fungal colonies is characterized as appearing mostly wrinkled?

  • Velvety or Silky (correct)
  • Granular or Powdery
  • Moist
  • Cottony or Woolly

    • What is a primary disadvantage of using KOH or LPCB in fungal colony sampling?

  • It can damage the vegetative spores.
  • It is not effective for systemic fungi sampling.
  • It limits sampling to reproductive spores only. (correct)
  • It destroys the morphology of the fungi.

    • Where is the best place to observe the pigmentation of fungi?

  • On the top surface of the medium
  • Under bright light
  • On the underside of the medium (correct)
  • In the surrounding environment

    • What is a primary advantage of the hair baiting technique in fungal culture sampling?

    <p>It does not destroy the morphology of the fungi.</p> Signup and view all the answers

    What is primarily observed when sampling fungal colonies?

    <p>The color of the pigmentation</p> Signup and view all the answers

    Which type of surface texture of a fungal colony is described as cottony or woolly?

    <p>A fluffy and soft texture</p> Signup and view all the answers

    What form do dimorphic fungi take at 37°C?

    <p>Yeast</p> Signup and view all the answers

    What is the optimum temperature range for saprophytic molds?

    <p>20-30°C</p> Signup and view all the answers

    Which feature is characteristic of molds?

    <p>Multicellular</p> Signup and view all the answers

    How long should fungal cultures be incubated for optimal growth?

    <p>21 days</p> Signup and view all the answers

    What type of reproduction do molds use?

    <p>Both sexual and asexual</p> Signup and view all the answers

    What is the standard incubation temperature for fungi?

    <p>30°C</p> Signup and view all the answers

    Which of the following is NOT a form of fungal growth?

    <p>Bacteria</p> Signup and view all the answers

    What factor can induce a dimorphic fungus to change its form?

    <p>Change in temperature</p> Signup and view all the answers

    What is the typical growth temperature range for parasitic fungi?

    <p>30-37°C</p> Signup and view all the answers

    What process forms a new yeast cell?

    <p>Budding</p> Signup and view all the answers

    What happens to a yeast bud once it has formed?

    <p>It remains attached until it splits.</p> Signup and view all the answers

    What is binary fission in the context of yeast?

    <p>A method where DNA is duplicated and the cell divides.</p> Signup and view all the answers

    Which of the following represents how a yeast cell duplicates its genetic material?

    <p>Replication</p> Signup and view all the answers

    Which type of diseases can Griseofulvin be used against?

    <p>Mycosis</p> Signup and view all the answers

    What type of bacteria can cephalosporin target?

    <p>Both Gram+ and Gram- bacteria</p> Signup and view all the answers

    What is typically true about higher fungi?

    <p>They can be consumed directly as mushrooms.</p> Signup and view all the answers

    How does a yeast cell ensure that each new organism receives DNA during division?

    <p>By duplicating and then splitting DNA.</p> Signup and view all the answers

    During mitotic division, what is the phase where the cell divides its cytoplasm called?

    <p>Cytokinesis</p> Signup and view all the answers

    Which characteristic describes budding in yeast?

    <p>It produces identical offspring.</p> Signup and view all the answers

    What type of hyphae do Penicillium exhibit?

    <p>Septate hyphae</p> Signup and view all the answers

    Which structure is characteristic of Rhizopus?

    <p>Sporangium</p> Signup and view all the answers

    What is the function of phialides in fungi like Penicillium?

    <p>Produce conidiospores</p> Signup and view all the answers

    Which of the following fungi has nonseptated hyphae with no rhizoids?

    <p>Mucor</p> Signup and view all the answers

    Which of the following statements is true about Phialophora?

    <p>It has septate hyphae.</p> Signup and view all the answers

    What are the structures in Rhizopus that support the sporangium?

    <p>Sporangiophores</p> Signup and view all the answers

    In which fungi are conidiospores arranged in chains?

    <p>Penicillium</p> Signup and view all the answers

    What type of hyphae is characteristic of Mucor?

    <p>Coenocytic hyphae</p> Signup and view all the answers

    Which fungal structure is flask-shaped and contains conidiospores?

    <p>Phialide</p> Signup and view all the answers

    What is the role of sporangiophores in fungi?

    <p>Support for the fruiting body</p> Signup and view all the answers

    What characteristic do dematiaceous fungi exhibit?

    <p>They produce melanin in their cell walls.</p> Signup and view all the answers

    What type of patients are most commonly affected by fungal meningitis caused by dematiaceous fungi?

    <p>Immunocompromised patients</p> Signup and view all the answers

    Where are dematiaceous fungi commonly found?

    <p>In pigeon droppings</p> Signup and view all the answers

    What is used to identify the capsule of Cryptococcus neoformans?

    <p>India ink wet mount</p> Signup and view all the answers

    What visual characteristic indicates dematiaceous fungi when hyphae are observed?

    <p>Brown color</p> Signup and view all the answers

    What does a clear halo against a dark background indicate in the India ink preparation?

    <p>The presence of a fungal capsule</p> Signup and view all the answers

    Which of the following describes the colonies of dematiaceous fungi?

    <p>Dark and pigmented</p> Signup and view all the answers

    What type of staining method is demonstrated by using India ink?

    <p>Negative staining</p> Signup and view all the answers

    What type of fungal infection can dematiaceous fungi cause?

    <p>Meningitis among immunocompromised patients</p> Signup and view all the answers

    A sample observed with brown-colored hyphae would most likely be categorized as what type of fungus?

    <p>Dematiaceous fungi</p> Signup and view all the answers

    Study Notes

    Molds

    • Are multicellular
    • Have a filamentous, branching form
    • Grow at room temperature

    Dimorphism vs. Monomorphism

    • Dimorphic fungi are able to exist in both mold and yeast forms
    • This change is usually triggered by environmental conditions, such as temperature
      • For example, they exist as yeasts at 37°C (body temperature) and molds at room temperature
    • Thermally dimorphic fungi are an example of dimorphism

    Fungal Cultures

    • Saprophytes (molds) have an optimal temperature for growth of 20-30°C
    • Parasitic fungi (yeasts) have an optimal temperature for growth of 30-37°C
    • The standard incubation temperature for fungal cultures is 30°C
    • Fungal cultures are incubated in a humidified environment for 21 days
    • Bacterial cultures require an incubation temperature of 37°C

    Fungal vs Bacterial Cultures

    • Fungal cultures are clinically important in the diagnosis and treatment of fungal infections
    • Anti-fungal medications are used to treat infections caused by fungi

    Fungal Reproduction

    • Fungi can reproduce sexually or asexually
      • Asexual
        • Budding: a new cell is formed through mitotic division and remains attached to the parent cell until it splits
        • Binary fission: a yeast cell replicates its genetic material (DNA) and then divides into two parts, with each receiving one copy of DNA
    • Sexual: Involves the fusion of gametes or nuclei from two parent organisms, resulting in the formation of spores.

    Dematiaceous Fungi

    • Produce melanin in their cell walls
    • Have a characteristic brown color when grown on agar
    • Have dark colonies and pigmented fungal elements
    • India Ink Wet Mount: used to identify the capsule of Cryptococcus neoformans (a dematiaceous fungus)
      • CSF is examined by adding one drop of India ink
      • The capsule appears as a clear halo against a dark background (negative staining)

    Penicillium

    • Septate hyphae with a conidiophore that exhibits branching to form metulae
    • Brush-like conidiophore (metulae) give rise to phialides with conidiospores
    • Spores are arranged in chains

    Phialophora

    • Septate hyphae with flask-shaped phialides with cup-shaped collarettes with conidiospores
    • NO CONIDIOPHORE

    Rhizopus

    • Nonseptated hyphae
    • With rhizoids (root-like structures)
    • With sporangiophores (stalk-like structures)
    • With sporangium (sac-like structure)

    Mucor

    • Nonseptated hyphae with no rhizoids
    • Sporangiophores arise singly with a sac called sporangium
    • Sporangium contains sporangiospores

    Topography of Fungal Cultures

    • It's important to observe the surface texture and pigmentation of fungal colonies.
    • Surface texture can be:
      • Cottony or woolly
      • Velvety or silky
      • Granular or powdery
      • Moist
    • Pigmentation can be observed on the surface or on the reverse side of the culture medium
    • Cellophane Tape Preparation:
      • Used to sample sporulating fungi
      • A cellophane tape is placed on the fungal culture and lifted
      • The tape is then put on a slide with KOH or LPCB
      • It's good for sampling sporulating fungi but may not show hyphae or rhizoids
      • Advantage: does not destroy the morphology of fungi
      • Disadvantage: limited to sampling reproductive spores and not vegetative spores

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    Description

    Explore the fascinating world of fungi, focusing on molds and their growth conditions. Learn about dimorphism, the difference between fungal and bacterial cultures, and the significance of environmental factors in fungal growth. This quiz is ideal for students of microbiology and mycology.

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