Summer Research Program for Science Teachers

Ayorinde Ayetiwa

Washington Irving High School

How To Culture Bacteria in the Laboratory

MATERIALS : plates, flasks, weighing balance, agar, trptone, Nacl, yeast extract, ampicillin, graduated cylinder

METHOD : take 15ml of water, dissolve the following compounds in the weighted amount :

NaCl (granular) 0.075g

Yeast extract 0.075g

Tryptone 0.150g

Agar 0.225g


Stir the mixture and autoclave for 25minutes at a temperature of 120 C

Pour solution into plate and allow to cool for 15 minutes. What do you observe?

Take a sample of dust (may be near the window) with the stick provided.

Streak by drawing a thin, zigzag, light line on the LB medium until the plate is covered with the lines containing the dust. Cover the plate. Place the plate in an incubator set at 37 C and leave overnight.

Prepare another LB medium in the same way as described and in addition add about ml of the prepared ampicillin to the LB in the flask.

Then transfer the solution on to the plate, allow to cool for about 15 minutes and streak with dust as described. Incubate and leave overnight. This is your control.

After 24hours record your observation. What happened to the plate containing ampicillin? [Content Standard Unifying Concepts- Change, constancy, and measurement]


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