How to T‐Streak (Microbiology)

Reviewed by Anne Schmidt

Last Updated: April 25, 2023

In nature, bacteria are found on practically every surface imaginable and unfortunately rarely exist in isolated populations containing a singular species of bacterium. This presents microbiologists with an interesting challenge obtaining isolated colonies of bacteria in a method that is both simple and rapid. The three sector streak or commonly referred to as the “T-Streak” is a basic, yet crucial skill used by microbiologist on a daily basis to isolate, identify, and study colonies of bacteria.

Part 1

Part 1 of 5:

Drawing the T

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Draw a line starting slightly above the center point. Continue drawing the line until you hit the back plate's edge.
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This new line should be perpendicular to the original line, intersecting it at the starting point. The back plate of the petri dish should now be divided into three sectors, appearing as a large “T”.

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Label the back plate of the petri dish with relevant laboratory information such as your initials, date, time and culture source.

Part 2

Part 2 of 5:

Sterilizing the Inoculation Loop

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In order to eliminate the chance of contaminating the petri dish when inoculating the surface of the agar in the petri dish, the inoculation loop must be sterilized.