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How does the Pour Plate Method work?

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Agar in bottles and tubes is used to pour plates or to generate an overlay on existing agar.

Preparing the agar:

  1. Melt the agar at 95°C in a water bath or using saturated steam (autoclave). Do not forget to open slightly the screw cap.
  2. Let the agar cool down in a water bath at 47-50°C.
  3. Media added to the sample should be tempered to 44-47°C.
  4. Do not use a microwave. The bottles might explode.

The table below gives an estimate on melting times (max. 4 hours) and cooling times:

  1. Volume of Agar
    Melting time
    Cooling time
    (47-50°C)
    up to 25 ml 10 min max. 4 h
    200 ml 45 min max. 4 h
    400 ml 60 min max. 4h

Do not use the pour-plate method for microorganisms, which are temperature-sensitive.

Pipette 0,1 ml - 1 ml containing 30 - 300 cfu into an empty sterile plate. Add 18 - 25 ml of the agar and mix gently. Incubate the agar as usual.

Do not reuse melted agar a second time after solidifying.

Incubation

Incubate plates upside down to avoid condensation water on the agar surface. Do not pile more than 6 plates to ensure constant incubation conditions.