How Do You Count Colonies? Colony Counting for Beginners

There are a few different methods for counting colonies, but a colony counter is ideal. In this YouTube video, the speaker goes over the different methods of colony counting for beginners. Counting colonies using a colony counter involves a few simple steps:

Prepare the Petri dish: After incubating the agar plate containing the bacterial colonies, place it on a flat surface under proper lighting conditions.

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The colonies should be visible and distinct.

Set up the colony counter: Switch on the colony counter device. Adjust the light intensity and focus as needed to clearly see the colonies.

Position the Petri dish: Place the Petri dish containing the colonies under the lens of the colony counter. Ensure it is positioned properly and stable.

Counting: Using the counting pen or cursor of the colony counter, touch each colony on the agar plate. As each colony is touched, the counter will increment by one, keeping track of the total count.

Record: Note down the count as you go, or the colony counter might have a feature to save the count digitally.

Verification: Once you’ve counted all visible colonies, it’s often a good practice to double-check your count to ensure accuracy.

Cleaning: After counting, clean the surface of the Petri dish and the colony counter to prevent contamination between samples.

Remember to practice good aseptic technique to avoid contamination of your samples during the counting process.


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