To streak plates you will need an inoculating loop or needle.
Inoculating needles for professional use are made with platinum wire
and cost $50.00 or more.
There are commercially available disposable inoculating loops. They
are made of plastic and cannot
be flame sterilized. They should be used once and discarded.
You can also just make your own.
Inoculating loop: The Paper Clip Version
* Unfold the large loop of a jumbo sized paper clip.
* Criss-cross the small end loop into a loop as shown.
Use the large loop as a handle and the small loop to seed or inoculate
the media
with the bacteria or other micro-organism.
Inoculating needle: The Sewing Needle-Pencil Version
* Stick the point of a sewing needle into the end
of the eraser of a pencil.
Inoculating loops (unless disposable plastic) and needles should be
sterilized in a flame between each plate.
Metal loops and needles should be sterilized by holding them in a flame
until the tip glows red hot.
A candle or alcohol burner can be used for the heat. Cool the metal
in sterile water after each flaming.
Streaking the plates.
Suspend the micro-organisms in 1 ml of distilled water in a test tube.
Stir the suspension with a sterile inoculating loop or needle.
Lift the cover of the sterile media prepared petri dish.
Hold the loop or needle at a shallow angle to the dish.
Streak (gently draw) the plate in a systematic pattern.
Close the dish immediately.
Seal the perimeter of the petri dish with a thin strip of parafilm
or plastic wrap.
Be sure to leave the top of the petri dish clearly
visible for observations and photography.
Sterilize the loop or needle and continue with the next plate until
all of the plates are inoculated.
Set aside some plates as controls.
Organisms growing where you streaked the plate are those that you inoculated.
Organisms growing elsewhere on the plate come from contamination.
Organisms growing in control plates that were streaked with a sterile
needle means you have contamination problems.
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