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now: Sat Jun 25 10:07:06 2022 ... mod: Mon Mar 29 07:39:56 2021
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Streak for Isolation

From a culture of mixed or concentrated bacteria, dilute the sample by streaking on an agar plate so that colonies arising from individual cells can be isolated.

  1. sterilize a bacterial loop by flaming
  2. allow the loop to cool slightly and gather a small sample of either bacterial culture or a small scraping of a frozen bacterial stock onto the loop
    • for frozen stocks, do not allow the stock to thaw
  3. streak the loop across the top of a bacterial agar plate in three parallel lines
    • the lines should be fairly close together
    • streak using the wide part of the loop, not the edge of the loop
  4. flame sterilize the loop and cool by stabbing a clean part of the agar plate
  5. make three new parallel streaks starting by going across the last part of the previous three streaks and continuing onto a clean part of the plate
    • repeat the last two steps three or four times being careful to only contact the immediately previous streaks and not earlier streaks
  6. grow at 37C overnight


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