Klapperich Lab:Streaking bacteria on Agar plate

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This protocol describes the procedure for streaking bacteria on an Agar plate.


  • Agar plate(s)
  • Bacteria sample from old plate
  • Inoculation loop
  • Bunsen Burner
  • 70% Ethanol
  • Parafilm


  1. Wipe down the bench with 70% EtOH and start a Bunsen burner flame.
  2. Label new agar plate(s), on the bottom, with your initials, the date and strain of bacteria, and prepare plastic beaker for containing the disposable at the side.
  3. Flame until red to disinfect the inoculation loop, from top toward the loop, and allow it to cool down by inserting to loop into the agar at a corner of the new agar plate.
  4. (work by the flame) Open the old streaking plate, wipe down water vapor on the cover with Kimwipes, and take one (1) pure culture with the loop.
  5. Slide the loop over the new agar plate. First start circulating ~10 times at a corner of the streaking area, followed by moving the loop in zigzag patterns to spread the colony on all 4 quadrants over the plate. Between each spread, flame the loop to disinfect and allow it to cool down. Cross over the previous quadrant 2~3 times and avoid cross over the previous quadrant more than once or into any other quadrants for the last streak.
  6. Cover the new dish and seal the edge of the old plate with parafilm.
  7. Incubate the new plate @37C in a upside-down position overnight (~24hrs)
  8. Bleach and wipe down the bench with 70% EtOH again at the end.
  9. Take the plate(s) out from the incubator on the next day and store it inside the fridge with parafilm sealing the edge.
  10. Bleach the old dish (entirely cover the plate) and seal with parafilm. Dispose it in the biohazard trash.


  1. The new streaking plate is good for a month. Bacteria needs to be re-streaked every month.
  2. Streaking plate should be always stored in upside-down position to allow water to drip onto the cover.



Sylvanus Lee