High Sieran lake. Photo©CLCase

 

 

Bacteriologic Quality of Water
An environmental project
Christine L. Case

My home page Skyline Biology

 

About the MPN test
For further study
MPN table
Sample problems		 Lab Protocol
  1. Label three single-strength lactose broth tubes "0.1," label another three tubes "1," and label three 1.5-strength broth tubes "10."
  2. Inoculate each "0.1" tubewith 0.1 ml of your water sample.
  3. Inoculate each "1" tube with 1.0 ml of your water sample.
  4. Inoculate each "10 " tube with 10 ml of the water sample. Why is 1.5-strength lac-tose broth used for this step?
  5. Incubate the tubes for 24 to 48 hours at 35°C.
  6. Record the results of your MPN test. Which tube has the highest dilution of the water sample? Determine the number of coliforms per 100 ml of the original sample using MPN table for the 9-tube method or the 15-tube method.