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STAINING

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Termini in questo insieme (20)

  • Purpose of staining in microbiology
    Staining provides contrast to promote visibility of bacteria under the microscope.
  • Three key features of a microscope for viewing bacteria
    Magnification, resolution, and contrast.
  • Difference between simple and differential staining
    Simple staining uses one stain to show shape and arrangement; differential staining uses multiple stains to identify bacteria by cell wall characteristics.
  • Four essential steps in bacterial staining procedure
    1. Smear preparation, 2. Air dry, 3. Heat fixation, 4. Staining.
  • How to prepare a smear from broth culture
    Use a sterile inoculation loop to place a loopful of broth on a clean slide and spread thinly over an area the size of a dime.
  • How to prepare a smear from solid culture
    Place a drop of water or saline on slide, transfer bacteria from colony with loop, mix in circular motion to size of a nickel.
  • Purpose of heat fixation
    Kills bacteria and affixes the smear to the slide so it does not wash off during staining.
  • Components of a chromogen in staining
    Chromogen has a chromophore (color generating) and an auxochrome (charged component that binds cells).
  • Difference between basic and acidic dyes
    Basic dyes are positively charged and stain negatively charged bacterial surfaces; acidic dyes are negatively charged and stain the background (negative staining).
  • What is positive staining?
    Staining where the microbe surface is stained due to attraction of basic dyes to negatively charged cells.
  • What is negative staining?
    Staining where the background is stained by acidic dyes, leaving cells unstained and visible.
  • Common bacterial shapes observed in simple staining
    Coccus (round), Bacillus (rod-shaped), Spiral forms including vibrio, spirillum, and spirochete.
  • Description of coccus bacteria
    Spherical or round-shaped bacteria.
  • Description of bacillus bacteria
    Rod-shaped bacteria.
  • Types of spiral bacteria
    Vibrio (comma-shaped), spirillum (curved or spiral), and spirochete (corkscrew-shaped).
  • Common bacterial arrangements of cocci
    Diplococcus (pairs), streptococcus (chains), tetrad (groups of four), sarcina (cubical packets), staphylococcus (clusters).
  • Common bacterial arrangements of bacilli
    Diplobacilli (pairs), streptobacilli (chains), palisades (side-by-side arrangement).
  • Steps after staining to observe bacteria
    Air dry stained slide, blot residual water, observe under microscope starting at 4X then 10X and 40X objectives.
  • Why is smear made thin during preparation?
    To allow clear observation of bacterial morphology under the microscope.
  • Role of auxochrome in staining
    It is the charged component of the chromogen that forms bonds with bacterial cells.