Fungi: Molds & Yeasts Overview
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Questions and Answers

Which statement accurately describes the structure of non-septate hyphae?

  • It allows streaming of cytoplasm through septa.
  • It has cross-walls that separate individual cells.
  • It forms a dense mat of mycelium only.
  • It is characterized by continuous filaments without cross-walls. (correct)

    • What is the primary means by which yeasts reproduce?

  • Fragmentation
  • Hyphal extension
  • Binary fission
  • Budding (correct)

    • How do septate hyphae facilitate the growth of mold colonies?

  • By allowing individual cells to maintain separation.
  • By allowing for cytoplasm streaming through pores. (correct)
  • By blocking nutrient absorption.
  • By directly forming the mycelium structure.

    • What infection is primarily associated with Candida albicans?

    <p>Thrush in newborns</p> Signup and view all the answers

    What is a distinguishing feature of yeast compared to molds?

    <p>Yeasts reproduce primarily through budding.</p> Signup and view all the answers

    Which substance is used to disinfect work surfaces in the lab?

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

    What process describes the introduction of microorganisms into a culture medium?

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

    Which of the following best describes media used for microbial growth?

    <p>Nutrient-rich substances that can be liquid, solid, or semi-solid.</p> Signup and view all the answers

    What color indicates a positive result in a citrate test?

    <p>Royal blue</p> Signup and view all the answers

    What is the expected color change in a urease test for a positive reaction?

    <p>Hot pink/fuchsia</p> Signup and view all the answers

    How can you identify the presence of catalase in a culture?

    <p>By detecting bubble formation after adding H₂O₂</p> Signup and view all the answers

    Which type of bacteria produces green metallic colonies on EMB agar?

    <p>Gram-negative bacteria that rapidly ferment lactose</p> Signup and view all the answers

    What type of hemolysis is characterized by the smallest ring around a colony on a blood agar plate?

    <p>Alpha hemolysis</p> Signup and view all the answers

    What bacteria is specifically identified using the coagulase test?

    <p>Staphylococcus aureus</p> Signup and view all the answers

    What does Mannitol-Salt Agar selectively isolate?

    <p>Staphylococcus species</p> Signup and view all the answers

    What is the purpose of performing an oxidase test before using the Enteropluri test system?

    <p>To assess if bacteria are oxidase-positive or negative</p> Signup and view all the answers

    What is the primary purpose of culturing microorganisms?

    <p>To intentionally grow microorganisms for study or production</p> Signup and view all the answers

    Which type of culture media is NOT considered solid?

    <p>Nutrient-rich broth</p> Signup and view all the answers

    What is the primary function of iodine in the Gram stain process?

    <p>To enhance binding of the primary stain to gram+ cells</p> Signup and view all the answers

    Which characteristic indicates a pure culture when observing colonies?

    <p>Consistent shape, size, and color across colonies</p> Signup and view all the answers

    How can the number of cells on a countable plate be calculated?

    <p>(Number of colonies / 100) * 10^Dilution factor</p> Signup and view all the answers

    What is the purpose of using a higher-power objective lens in microscopy?

    <p>To enhance magnification and detail of fine structures</p> Signup and view all the answers

    What technique is used to observe the motility of microorganisms?

    <p>Hanging drop technique</p> Signup and view all the answers

    What does the term 'ubiquitous' refer to in the context of microorganisms?

    <p>Microorganisms found in nearly every environment</p> Signup and view all the answers

    What should you avoid doing when handling the needle end of the tube?

    <p>Touching the needle end with your hands</p> Signup and view all the answers

    What action should you take to ensure anaerobic conditions in the Enteropluri tube?

    <p>Break the wire at the designated notch</p> Signup and view all the answers

    What result indicates a positive glucose reaction in the Enteropluri test?

    <p>Complete separation of wax overlay from medium</p> Signup and view all the answers

    How should you analyze the biochemical reactions after incubation?

    <p>All chambers should be examined for color changes</p> Signup and view all the answers

    What does a purple result in the lysine decarboxylase (LYS) chamber indicate?

    <p>Decarboxylation of lysine has occurred</p> Signup and view all the answers

    What is the recommended incubation temperature and duration for the Enteropluri tube?

    <p>37°C for 18 - 24 hours</p> Signup and view all the answers

    Why is it important to make holes in the plastic coverings of the depressions in the last eight compartments?

    <p>To enable anaerobic growth</p> Signup and view all the answers

    What should be done with the wire after making holes in the chambers?

    <p>Dispose of it in a biohazard bag</p> Signup and view all the answers

    What color indicates a positive result for the ornithine decarboxylation test?

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

    What is the result of a successful indole formation test after adding Kovac's reagent?

    <p>Pink/Red</p> Signup and view all the answers

    In the testing for H2S production, which color indicates a positive result?

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

    What is considered a potable level of coliform colonies in a water sample?

    <p>1 coliform colony/100ml or less</p> Signup and view all the answers

    Which component of the laboratory procedures helps to inhibit gram-positive bacteria while allowing gram-negative bacteria to grow?

    <p>EMB agar plate</p> Signup and view all the answers

    What color result indicates an alkaline condition for the urea test?

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

    During serological typing using the slide agglutination test, what is being identified?

    <p>Microbial species using specific antibodies</p> Signup and view all the answers

    If both DUL and PA tests are positive, which of the following is true?

    <p>It is impossible for both to be positive.</p> Signup and view all the answers

    Study Notes

    Fungi: Molds & Yeasts

    • Molds form colonies from microscopic, intertwined filaments called hyphae.
    • Hyphae are either septate (separated by cross-walls) or non-septate (no cross-walls).
    • Growth occurs at hyphae tips, forming a branching network called mycelium.
    • Mold colonies appear as a mat of hyphae on substrate.
    • Yeasts are fungi that do not typically form hyphae.
    • Yeasts reproduce by budding, where a new cell forms and separates from the parent.
    • Candida albicans is a yeast that can cause infections in humans, especially newborns.

    Mold Identification

    • Inoculation is the introduction of microorganisms into a growth medium.
    • Various media include nutrient-rich agar, blood agar, MacConkey agar, mannitol salt agar, and eosin methylene blue agar (EMB).

    Microbial Culture Techniques

    • Procedures for disinfection of work surfaces are essential.
    • Proper inoculation techniques (e.g., streaking on agar slants, swabbing) are crucial for isolating pure cultures.
    • Techniques for observing microbial motility (hanging drop method) and microscopic observation are used.

    Gram Stain Process

    • Gram stain is used to differentiate bacteria by their cell walls.
    • Crystal violet stains all cells purple (primary stain).
    • Iodine forms a complex with crystal violet, enhancing binding (mordant).
    • Ethanol decolorizes gram-negative cells, leaving them colorless.
    • Safranin stains decolorized cells, making them pink/red (counterstain).

    Bacterial Count Calculation

    • Bacterial counts are determined from dilution plates.
    • Count colonies on a plate with a countable number of colonies(30-300).
    • Use the formula: (number of colonies on plate) x (dilution factor of the plate) = number of cells per ml

    Specific Tests

    1. Urease Test: Positive result appears as hot pink/fuchsia.
    2. Catalase Test: Presence of bubbles indicates positive result.
    3. Hemolysis Test on Blood Agar: Different types of hemolysis include alpha, beta, and gamma.
    4. Coagulase Test: Used to identify Staphylococcus aureus.
    5. Mannitol Salt Agar (MSA): Selective and differential medium for Gram-positive bacteria, especially Staphylococcus.

    Membrane Filtration Method

    • Membrane filtration is a method for detecting coliforms to determine the potability of water.
    • Colonies are counted on EMB agar.
    • Less than 1 colony per 100 mL of water is generally considered potable.

    Slide Agglutination Test

    • Slide agglutination tests use antibodies specific to microbial antigens to identify microbial species.
    • A positive result causes clumping (agglutination).

    Enteropluri Test System

    • A single tube that incorporates 15 biochemical tests for identifying gram-negative bacteria.
    • Includes tests for carbohydrate fermentation, enzyme production, and gas production.

    Biochemical Reactions of Enteropluri Tests

    • Various tests are used including those for lactose, urea, glucose, H₂S production, indole, ornithine, and citrate.
    • Specific colors or production of gas in the wells/chambers indicate test results

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    Description

    Explore the fascinating world of fungi, focusing on molds and yeasts. Learn about the structure and growth of molds, including hyphae and mycelium, as well as the unique characteristics of yeasts like Candida albicans. This quiz covers key identification and culture techniques essential for studying these microorganisms.

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