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Microscopy and Staining in Microbiology

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Termini in questo insieme (20)

  • What is the total magnification formula for a compound light microscope?
    Total magnification = \(objective\ lens \times ocular\ lens\).
  • What is resolution in microscopy?
    Resolution is the ability of lenses to distinguish two points as separate.
  • Why is immersion oil used in microscopy?
    Immersion oil prevents light refraction between the glass slide and objective lens, improving resolution.
  • Describe brightfield microscopy.
    Brightfield microscopy shows dark objects against a bright background using regular illumination.
  • What is darkfield microscopy?
    Darkfield microscopy shows light objects against a dark background by blocking direct light with an opaque disk.
  • How does phase-contrast microscopy work?
    It combines direct and diffracted light rays to enhance contrast in living cells without staining.
  • What is a smear in microbiology?
    A smear is a thin film of microorganisms spread on a slide for staining and observation.
  • What is the purpose of heat fixing a smear?
    Heat fixing kills microorganisms and attaches them to the slide.
  • What is the difference between basic and acidic dyes?
    Basic dyes have a positively charged chromophore; acidic dyes have a negatively charged chromophore.
  • What is negative staining?
    Negative staining colors the background instead of the cells, highlighting capsules or delicate structures.
  • What is a mordant in staining?
    A mordant is a fixative that intensifies or improves the stain's color fastness.
  • What is the purpose of a simple stain?
    A simple stain uses one basic dye to highlight the entire microorganism for shape and structure visualization.
  • What are differential stains used for?
    Differential stains distinguish different types of bacteria based on their staining properties.
  • What are the main steps of Gram staining?
    Apply crystal violet, iodine mordant, alcohol decolorizer, then safranin counterstain.
  • How do Gram-positive and Gram-negative bacteria differ in cell wall structure?
    Gram-positive bacteria have thick peptidoglycan and teichoic acids; Gram-negative have thin peptidoglycan and an outer membrane with lipopolysaccharides.
  • What is the acid-fast stain used to identify?
    It identifies bacteria with waxy cell walls like Mycobacterium and Nocardia.
  • What colors do acid-fast and non-acid-fast bacteria appear after acid-fast staining?
    Acid-fast bacteria appear red; non-acid-fast appear blue after counterstaining.
  • What is the purpose of capsule staining?
    Capsule staining highlights the gelatinous capsule around some bacteria using negative staining.
  • How are endospores stained?
    Endospores are stained green with malachite green and heat, while vegetative cells are counterstained red with safranin.
  • Why is flagella staining used?
    Flagella staining thickens flagella with mordant and dye to make them visible under a light microscope.