How to use Spread Plate technique

Warm wishes from ‪@MicrobiologyMantra‬ .
This video explains about the spread plate technique which is one of the isolation methods and is very important. I hope this video provides all information you need. Please comment if you have any question.

Background music: www.bensound.com

Script from video:
Spread plate technique is one of the isolation methods. This technique is used to isolate and count microbial colonies from a liquid sample.

This technique is very useful in the microbial testing of food, and other environmental samples like soil and water.

If the sample that need to be tested is not in the liquid state, then it needs to be grinded, dissolved in suitable liquid, and then used for testing.

To perform this technique, we need test tubes, pipettes, glass spreader which is in L shape, Nutrient agar plates, Bunsen burner, and alcohol or acetone.

Let’s see how this is done.

Take out 0.1 millilitre of sample using a sterile pipette, and place it in the centre of the agar plate.

Here we forgot to mention one important step.

Before adding the sample to the plate, we have to prepare serial dilutions of the sample in order to bring the microbial cells to the countable number. We will discuss more about serial dilutions in our next video.

Now that we are ready with the sample dilutions, it is very important to label each plate with the dilution factor.

Ok. Now, after adding the sample to the plate, take the glass spreader, dip in to the alcohol or acetone, and expose to the flame in order to make it sterile.

Wait for a few seconds, and then spread the sample evenly all over the agar surface.

This can be achieved by gently rotating the plate, and holding the spreader at 45 degree angle. This enables us to operate the spreader smoothly and decreases the hand pressure on the agar surface.

We can also make use of a rotator to rotate the plate with more ease.

Ensure that the sample is distributed all over the agar surface.

Then incubate the plates at 37 degree celsius for 24 hours.

After the incubation period, you should see isolated and countable colonies distributed on the agar surface in one of dilutions.

With this count, we can calculate the population of microbes present in the original sample.