1. Designated and label three bottles already filled with 99 mL of water: A, B, and C.
2. Then Label the bottom half of four petri plates with “B: 1 mL H20”, “B: .10 mL H20”, “C: 1 mL H20”, and “C: .10 mL H20”.
3. Add 1 mL of E. coli to Bottle “A”. Cap it, and cover it with parafilm and use wrist to flick bottle away from face to mix. Count 25 flicks.
4. Open Bottle “A” after mixing and from it dispense out 1 mL of water using a new serological pipette
5. Transfer the 1 mL H20 to Bottle “B”. Cap this bottle, and cover with parafilm. Flick wrist 25 times to mix it.
6. Use the pipette to dispense 1 mL and .10 mL each from “Bottle B” to the two designated separate Petri plates. Cover plates and swirl gently. Set Aside.
7. Replace pipette with a new one and dilute “Bottle C” by adding 1 mL from “Bottle B” to it. Cap the bottle, protect it with parafilm and flick/shake it 25 times.
8. Use the pipette to dispense 1 mL and .10 mL each from “Bottle C” to the two designated separate Petri plates. Cover plates and swirl gently. Set Aside.
9. Collect four petri plates and to each pour 50oC liquid agar medium until the smaller half of the plate is sufficiently covered.
10. Gently swirl the plates to mix agar with diluted water and set aside for 10 to 15 minutes to allow it cool before incubating.
- Only Plate C with 1 mL had 103 colonies which is a significant number.