The Streak-Plating Technique


The text of the narration (read by the Apple Macintosh OS 9 "Victoria, high-quality" computer voice) is as follows:

Here we see the proper method for preparing a streak plate. The loop has already been dipped into the culture tube and is held perpendicularly to the surface of the medium. Note that the lid is lifted just enough to allow the loop to enter the plate. The loop is streaked back and forth across the surface of the medium, depositing fewer and fewer organisms as it goes.

So far we have only streaked across a half of the plate. Eventually we want to cover the entire plate.

Going back to the beginning, it can be handy to draw some lines on the bottom of the plate to deliniate the three phases of our streaking process. Only for clarity in showing the three-phase streaking process as we look down at our plate, we are committing the sin of leaving off the lid!

We use the loop to streak the inoculum across the plate, working our way from the edge of the plate to the center.

The loop is carefully flamed to get rid of excess organisms, and the plate is rotated a quarter turn counter clockwise. We can cool the loop by touching it to the medium. The inoculum for the second phase of streaking comes from the organisms which had been deposited in the first phase.

For the final phase, the loop is flamed again and the plate is rotated another quarter turn. Picking up organisms from the second phase, the third phase is streaked. Note for each of the three phases, we are always working from the edge of the plate toward the center.


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Page content was last modified on 6/18/14 at 2:00 PM, CDT.
John Lindquist, Department of Bacteriology,
University of Wisconsin – Madison