Micro Experiment 15 & 16

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  1. What is the purpose of performing the spread, streak, and pour plate techniques?
    To obtain a pure culture of isolated colonies.
  2. List the matierials needed and describe how you would use them in performing the spread plate technique.
    • Broth
    • stock culture
    • spreader
    • agar
    • loops
    • - Take a loop of stock culture transfer to the center of agar plate and spread it smoothly
  3. List the materials needed and ddescribe how you would use them in performing the streak plate technique
    • 1. broth 2. stock culture 3. loop 4. agar plate
    • -Take loop of stock culture transfer to the edge of 1st quadrant
    • -streak it over the surface with a zigzag pattern
    • -using the same loop streak into the 2nd quadrant with a zigzag pattern
    • -continue in the same way for 3rd & 4th quadrant
  4. In all routine laboratory work, petri plates are labeled on the bottom. why?
    So the culture will not get mixed up if the lids are label with information and are not replaced on proper plate.
  5. Why is it important to invert the petri plates during incubation?
    Moisture drops down from the lid to agar surface and moisture will condense on the surface of the lid and cause confluent growth instead of isolate colonies
  6. What does CFU stand for? Define CFU
    Colony Forming Unit- represents a pure colony form from a single cell
  7. In the streak plate technique, how are microorganism diluted and spreas out to form individual colonies?
    A dilution gradient is establish on the surface of the agar as the cells are deposited on the surface as the loop is zigzag across each of quadrants.
  8. Which area of the streak plate will contain the greatest amount of growth? The last amount of growth? Explain.
    Primary streak in 1st quadrant will have greatest amount and 4th quadrant will have the least
  9. Draw and label the growth curve for bacteria
  10. Does each discrete colony on a plate be used to start a pure colony from a single cell? Explain your answer
    Yes, is assumed that each individual colony is derived from a single bacteria cell. But we have no way to substantiate it.
Card Set
Micro Experiment 15 & 16
Spread plate, streak plate and differential media
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