Streak plates

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This is the most common method for inoculating a plate.

How to streak an agar plate
How to streak an agar plate
  1. With this method, a small amount of sample is placed on the side of the agar plate (either with a swab, or as a drop from an inoculating loop if the sample is a liquid).
  2. A sterile loop (flamed until red hot, then cooled by touching the agar away from the inoculated sample) is then used to spread the bacteria out in one direction from the initial site of inoculation. This is done by moving the loop from side to side, passing through the initial site.
    • can also use a sterile glass pipette
  3. The loop is then sterilized (by flaming) again and the first streaks are then spread out themselves.
  4. This is repeated 2-3 times, moving around the agar plate.

What should happen is that single bacterial cells get isolated by the streaking, and when the plate is incubated, the resulting colonies will each have started from just one bacterium.

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