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Introduction to Microbiology: Culture, Staining, and Microscopy

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Termini in questo insieme (22)

  • What is the purpose of growth media in microbiology?
    Growth media are mixtures of nutrients that support microbial growth in an artificial setting, allowing microbes to be cultured in the laboratory.
  • Name the three main physical forms of culture media.
    Culture media can be plates (solid), deeps (solid), slants (solid), or broths (liquid).
  • What is a microbial colony?
    A colony is a genetically identical clone derived from a single mother cell, containing millions or billions of cells.
  • Why is the quadrant streak technique important?
    The quadrant streak technique is used to isolate single colonies and determine if a culture is pure by separating mixed cultures into distinct colonies.
  • How do basic dyes work in staining bacteria?
    Basic dyes are positively charged and bind to the negatively charged bacterial cell surface, coloring the cells.
  • What is the role of acidic dyes in negative staining?
    Acidic dyes are negatively charged and are repelled by the negatively charged cell surface, staining the background instead of the cells.
  • What is a mordant in staining procedures?
    A mordant is a chemical that interacts with a dye to trap it on or inside a specimen, enhancing stain retention.
  • What information does simple staining provide?
    Simple stains use one dye to reveal size, shape, and cellular arrangement of microbes.
  • What are structural stains used for?
    Structural stains highlight specific cell structures like flagella, capsules, and endospores.
  • How does the Gram stain differentiate bacteria?
    The Gram stain differentiates bacteria based on cell wall properties into Gram-positive (purple) and Gram-negative (pink) groups.
  • What color do Gram-positive bacteria appear after Gram staining?
    Gram-positive bacteria appear purple due to their thick peptidoglycan cell wall retaining the crystal violet dye.
  • What is the purpose of the iodine step in Gram staining?
    Iodine acts as a mordant, forming a complex with crystal violet that traps the dye in Gram-positive cells.
  • What happens if the iodine step is omitted in Gram staining?
    Without iodine, Gram-positive bacteria may not retain the crystal violet and could appear pink, leading to incorrect results.
  • What is the acid-fast stain used to detect?
    The acid-fast stain detects bacteria with waxy cell walls rich in mycolic acid, such as Mycobacterium species.
  • How do acid-fast bacteria appear after staining?
    Acid-fast bacteria retain the red/pink primary dye after acid wash, while non-acid-fast cells lose it and take up the blue counterstain.
  • What is magnification in microscopy?
    Magnification is the ability to enlarge an image, calculated as objective lens magnification × ocular lens magnification.
  • Define resolution in microscopy.
    Resolution is the ability to distinguish two adjacent objects as separate and distinct.
  • Why is immersion oil used with the 100X objective lens?
    Immersion oil has the same refractive index as glass, preventing light refraction and improving resolution and image clarity.
  • Compare bright field and dark field microscopy.
    Bright field uses a solid cone of light and requires stained samples; dark field uses hollow cones of light and shows unstained samples as bright on a dark background.
  • What is the main difference between TEM and SEM electron microscopy?
    TEM passes electrons through thin specimens to produce 2D internal images; SEM scans the surface with electrons to create 3D surface images.
  • What is fluorescence microscopy used for?
    Fluorescence microscopy uses fluorescent dyes (fluorochromes) that absorb UV light and emit visible light to visualize specific structures or organisms.
  • What is immunofluorescence?
    Immunofluorescence uses fluorescent dyes linked to antibodies to specifically detect target microbes or molecules.