Micro Lab

  1. Slant-agar/bacterial
    created by agar that solidifies on an angle; this increases the surface area exposed for growing anaerobic bacteria
  2. Agar
    most widely used solidifying agent. Provides a solid surface for microbes to grow on. It is NOT a nutrient source for microbes. Few microbes can degrade this so it remains solid when microbes are grown on it.
  3. Disk diffusion method
    used in teaching laboratories to evaluate the efficiency of a chemical agent. A sterile disk or filter paper is soaked with a chemical and placed on an agar plate that has been seeded with a lawn of the bacterial test organism
  4. Zone of inhibition
    • can be measured in mm.
    • The clear region around the paper disc saturated on antimocrobial agent on the agar surface
  5. Kirby Bauer interpretation
    • widely used for determining the most effective antibiotic to use to treat an infection. To perform, the suspected organism is isolated in pure culture and is tested for its sensitivity to several antibiotics.
    • pink-Lactose=fermenting
    • not pink-no Lactose=no fermentation
  6. If an organism grows on MacConkey agar, what type of Gran stain result would you expect to see?
    Gram -
  7. Why is Sabouraud media selective for fungi rather than bacteria?
    It's low pH (about 5.6) is inhibitory to most bacteria.
  8. What common goal is achieved by tests such as microbial growth on starch plates and catalase tests?
    useful in microbial identification.
  9. If you grow bacteria on SIM media and you get a black color what does that tell you about the bacteria?
    Indicates that a breakdown of sulfur containing amino acids has occurred
  10. "Strain" of bacteria
    A genetically identical group of cells derived from a single cell.
  11. Two purposes of Mannitol Salt Agar?
    • Determining salt resistance & mannitol sugar use.
    • Mannitol Salt agar is used to differentiate between staph fermentors and non-fermentors. It also only allows growth of Staphyloccus.
  12. Hemolysins
    An enzyme that lyses red blood cells.
  13. What species of bacteria from the surface of your skin did you isolate on mannitol salt agar?
    Nose-Staphyloccus emidermis
  14. What is the name of the test most commonly used to determine which antibiotic should be used to treat an infection?
    Kirby Bauer method is widely used for determining the most effective antibioitic to use to treat an infection
  15. What is the name of the media used to test for antibiotic sensitivity?
    Mueller-Hinton agar is the standard medium for antibiotic sensitivity testing.
  16. Is DNA positively or negatively charged?
    DNA is negatively charged due to the negatively charged phosphate ions in its structure
  17. What group or atom in DNA gives the molecule its electric charge?
    The sugar-phosphate backbone of DNA gives it an overall negative charge.
  18. Why does DNA precipitate out of a solution when ethanol is added to it?
    Because the DNA is not soluble in ethanol
  19. Why is the enzyme Papain used in the DNA isolation protocal?
    It is a proteolytic enzyme that can break down proteins that were within the cell
Card Set
Micro Lab