Microbiology lab test

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  1. what are the 3 advantages of wet mounts
    • They can be used to view living organisms. 
    • Motility can be viewed.
    • Because they are not heat fixed; grouping of oragnisms is not disturbed.
  2. list steps of wet mount (2)
    • 1) Using pipet, place small drop of the liquid to be viewed in the center of a slide.
    • 2) Place cover slip over the drop, making sure it is droped at 45 deg angle and not straight down to avoid air bubbles.
  3. list steps of preparing a hanging drop wet-mount.
    • 1) hold slip cover with the fingers of one hand.
    • 2) with pipet place very small drop on slip cover.
    • 3) quickly invert slip cover over the depression of a depression slide.
  4. what are the advantages of staining microbes? (3)
    • Because of increased contrast microbes are easier to see.
    • Because a cover slip is not used, oil immersion can be used increasing the magnification.
    • Stained slides can be saved for future observation.
  5. What are the disadvantages of stained microbes? (2)
    • Because the microbes must be heat affixed to the slide which kills the microbes motility can not be seen.
    • The natural arrangment of bacteria will be disrupted as a result of the preparation of the slide.
  6. Describe the steps in preparing a smear from a broth
    • Make sure you are using a clean slide
    • If microbes are settled to the bottom of the tube gently agitate the tube shaking it from side to side not up and down.
    • Spread a loop full of broth about the size of a dime on the middle of the slide.
    • Air dry the slide never use the burner to dry.
    • Heat fix the slide by passing through the cone tip of the blue flame 3 times.
  7. describe the steps in preparing a smear from an agar surface
    • place a small drop of water on the slide.
    • remove the bacteria from the slant and spread them in the water to the size of a dime.
    • air dry
    • heat affix
  8. decribe the simple staining procedure.
    • place a few drops of metholyne blue over the smear and wait one minute.
    • holding the slide angled down over the sink slowly run water over it.
    • blot the slide with bulbous paper
  9. describe the steps involved in using the oil immersion objective.
    • get the bateria focused with the high-dry objective.
    • rotate objectives to in between high dry and oil immersion.
    • place a drop of immersion oil directly over condenser.
    • rotate immersion objective into place.
    • adjust the fine adjustment to focus.
    • after use discard slide into container on the counter.
    • clean objective with immersion oil cleaner and lens paper a few times.
  10. Describe the difference between a simple stain and a differential stain?
    a simple stain cannot differentiate between different bacteria and a differential stain can
  11. describe the goal of a gram stain procedure
    to differentiate between different bacterias
  12. steps of the gram stain procedure
    • 1 cover the smear with crystal violet wait 1 min rinse and shake. 
    • 2 cover the smear with grams iodine wait 1 min rinse and shake 
    • 3 cover smear with denatured alcohol wait 15 secs rinse and shake
    • 4 cover the smear with safranin wait 1 min rinse and shake
  13. what are the 4 staining agents used in gram staining and thier function
    • crystal violet - primary stain
    • grams iodine - mordant (reinforces attachment to cell wall)
    • ethonol - decolorizer
    • safrinin - counter stain
  14. what are some problems that could occur if a stain is done improperly or smear is too heavy.
    it could expierience grams variabilty where a slide appears to have both gram positive and gram negative. A heavy smear will also interupt the decolorizing step causing gram neg bacteria to appear gram pos.
Card Set:
Microbiology lab test
2013-03-18 17:40:08
maria college microbiology test

3 chapters micro test Prof. Radar
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