In this experiment that we performed, there were many methods that were used to help us manipulate and identify the bacteria E.coli on a MacConkey agar plate. The first part of the experiment involved the methods of manipulating, identifying and counting the bacteria and the second part was to find out whether the bacteria E.coli was the only type found in the given area by gram staining.
E.coli was the chosen bacteria for this type of experiment. It is a gram negative bacterium that will grow rapidly given ‘any culture medium with the necessary energy source, nutrients, pH, and temperature’. Therefore, MacConkey Agar being the medium for its growth will enable us to achieve the experiment …show more content…
You then spread out 100ul of the three dilutions onto the centre of different Agar plates using a loop and leave it to dry. This is to enable an evenly spread over the surface.
After incubation for a few days, the colonies should be formed on each Agar plate ready to be examined, counted and recorded.
Taking into account the dilution factor and the volume spread on each plate which is 100ul, the bacteria in 1ml of the original culture is calculated.
METHOD FOR GRAM STAINING
Choose your selected colony ready to use on a clean slide so that no contamination is made.
A drop of sterile saline is put onto the slide and the smear of the culture is mixed into it and spread it out thinly so that there is no overlap to enable clear image after staining.
Then leave it to dry so that it doesn’t drip and mess the area or slide and pass it two or three times under the Bunsen burner for the hydration of the remaining liquid.
Using the following gram staining method, stain the slide:
-Start by squirting with the crystal violet solution and leaving for about 30 seconds then rinsing off with water
-Then use Grams iodine solution and leaves for 30 seconds again and wash it off with water.
-The decolouriser stage is the third stage where acetone/alcohol is squirted and left only for about 5-10 seconds this time and rinse