lab test 4

  1. The simplest way to make a slide of bacteria is to prepare a
    wet mount
  2. Finding bacteria on a wet mount an be difficult for a beginner because bacteria are
    quite colorless and transparent
  3. a better way to observe bacteria for the first time is to prepare a slide by a process called
    negative or background staining.
  4. Negative staining consists of mixing the microorganisms in a small amt of ___________ and spreading the mixture over the surface of the slide.
    nigrosine or india ink
  5. These 2 pigments are NOT bacterial stains, they _________migroorganisms.
    Do not penetrate.
  6. Nigrosine & india ink ____________ to leave the organisms transparent & visible in the darkened field.
    Obliterate the background
  7. Although this technique has limitations, it can be useful for determining
    cell morphology & size
  8. Since no heat is applied to the slide, there is
    • no shrinkage of cells
    • (and more accurate cell-size determinations result than with some other methods.)
  9. Negative staining is also useful for _______________that dont stain readily with ordinary dyes
    studying spirochaetes.
  10. When studying bacteria using a negative stain,
  11. When using this method, make the smear thick at one end and feather-thin at the other, the ideal spot to study the organisms is
    somewhere in between the thick & thin areas.
Card Set
lab test 4
quiz 4, negative staining