Question

8. Using a hydrophobic grid membrane filtration system, you filtered 800 ml of processing water and placed the grid on an agar plate. After appropriate incubation procedures, you counted 26 colonies on the grid. How many colony forming units were there (per ml) in the original sample?

Answer 1

Solution:

Filtered water sample volume, V = 800 ml

After incubation procedures, number of colonies on the grid = 26 colonies

Therefore, number of colony forming units per ml in the original sample

= (26 colonies) /800 ml

= 0.0325 colonies/ml