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Streak Plate Method – Amrita University

August 25, 2019


Streak-Plate Method: Streak plate method is a pure culture technique
which helps in isolating desired colonies from contaminants.
The procedure begins by sterilizing a wire loop in flame.
Cool the sterilized loop by allowing it to stand for a few seconds.
Dip the loop into a sample containing a mixture of bacteria. Depending on the sample, the
loop may pick up hundreds or thousands of bacteria, which are spread back and forth
across the surface of the agar. Make a uniform smear with the inoculum at
the edge of the plate. Sterilise the loop as mentioned above, and
make streaks from the smear. Since there is thinning of inoculum during
streaking, isolated colonies are formed at ideal streak point where the spreading has
separated the individual (or group) of cells at locations where they can form individual
colonies The pattern of streaking varies with different
type of streak plate techniques, for e.g. Quadrant streak, T-streak etc.
During the incubation, the bacteria multiply and produce colonies.
Intermittent flaming of the loop can be done during streaking to reduce the load of the
organism so that there is a better chance of getting isolated colonies.
Keep the plate covered as much as possible to avoid contamination
While streaking a section of the plate, try to keep the inoculating loop in contact with
the surface of the agar at all times.

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