I am not really sure how to find the original concentration of bacteria for my experiment. This is what i did: I made serial dilutions of 10^-2, 10^-4,10^-6, 10^-8 with stock bacteria. From 10^-4 dilution, I took out 2ml and inoculated into 20g potatoes + 180g buffer. Potatoes + buffer + inoculum were homogenized. Then I took 0.1 ml from the homogenate and plate onto agar. If i want to find the original concentration in my stock bacteria, is this what I do: plate count = 30 colonies (30 x 10^4) / (10)(2) = 1.45x10^6 cfu/ml can someone check if my calculations are correct? Thanks!