Lab midterm

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Lab midterm
2011-02-08 20:22:14
Lab midterm

Lab midterm
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  1. If the chromophore is a positive ion like the methylene blue, the stain is considered
  2. Most bacteria are stained when
    a basic stain permeates the cell wall and adheres by weak ionic bonds to the negative charge of the bacterial cell
  3. Simple stain
    staining procedure that uses only one stain
  4. Direct stain
    simple stain that stains the bacteria
  5. Negative stain
    simple stain that stains the background but leaves the bacteria unstained
  6. Staphylococcus epidermidis
    round cluster
  7. Bacillus megaterium
    big rod
  8. Which bacterium is a rod
  9. Of what value is a simple stain
    show size and morphology
  10. What is the purpose of fixing the smear
    help cells stick to slide so that they can be stained
  11. In heat fixing, what would happen if too much heat were applied
    • Too much heat would cause the cell's shape to distort.
    • Denatures bacterial enzymes that cause the cells to break
  12. Methylene blue can be prepared as a basic stain or an acidic stain. How would the pH affect the staining of bacteria
    The pH will determine if the bacteria will have a particular charge
  13. Can dyes other than methylene blue be used for direct staining
    Yes. Crystal violet, basic fuchsin, and safranin are all dyes that can be used in direct staining because they are cationic which means they are positively charged
  14. Bacteria can be seen without staining. Why then was Koch's recommendation for fixing and staining important in microbiology?
    Allows bacteria to be saved and reexamined or shared