WHAT HAVE I LEARN?
This week is the last experiment conducting for the sem 1. We doing on the Experiment 18, Serial Dilution- Agar Plate Procedure to Quantitate Viable Cells. There are many methods in taking measurement of quantity of microbes in particular medium, including direct microscopic counts, electronic cells counter, chemical method, spectrophotometric analysis and also the Agar Plate Analysis. However the best way to gets the number of colonies for viables cells is through the Agar Plate Analysis.
Greater manipulation are needed for doing this experiment, we must be always clear on the dilution of the E. coli culture. This method involve serial dilution which the bacterial suspension in sterile water blanks. After dilution have done, the culture will be transfer to Petri dish by using pour plate technique or spread plate technique. For pour plate technique, the cooled Molten agar of 45°C is added to the Petri dish containing 1.0ml of bacterial suspension. The Petri dish is then gently rotated in a circular motion to make sure that all the bacterial cells are evenly distributed. For spread plate technique, the 0.1ml of bacterial suspension is carefully added into the Petri dish containing pre-prepared agar nutrient and is rotated using L-shaped glass rod in a circular motion. The average count per ml of sample is taken for both spread plate and pour plate. The number of organisms per ml of original culture is calculated by multiplying the number of colonies counted by the dilution factor:
Number of cells per ml= number of colonies x dilution factor
The Quebec colony counter and machanical hand counter is used in obtaining the number of colonies appear on the Petri dish. We can see that the bacterial colonies will grow on the surface and also suspended inside the nutrient medium for the pour plate technique. The Petri dish using spread plate technique only shows bacterial grow on the surface of agar.
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| This is Quebec colony counter. |
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| Final dilution of 10-7 |
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