An original sample of water containing 4.20 X 109 CFU/mL was diluted by 4 successive 1/100 dilutions. Exactly 1 mL from the last dilution was used to prepare a pour plate. After incubation, how many colonies were present on this plate?

A bacterial culture has a concentration of 3.2 x 108 cells /mL.  You dilute this culture as follows: 1/50, then 10-3 and finally 1/20.  If you then plate 0.2 mL of the final dilution, how many CFU would you expect following incubation?

You plated 1.0 mL of a sample diluted by a factor of 10^-5 and you counted 50 comonies after incubation. The concentration of bacteria in the stock culture is: A) 5x10^5 B) 5x10^4 C) 50x10^4 D) 50x10^-6 E) 5x10^-4

Ten grams of hamburger were added to 90 mL of sterile buffer. This was mixed well in a blender. One-tenth of amL of this slurry was added to 9.9 mL of sterile buffer. After thorough mixing, this suspension was further dilutedby successive 1/100 and 1/10 dilutions. One-tenth of a mL of this final solution was plated onto Plate Count agar.After incubation 145 colonies were present. How many colony-forming units were present in the total 10 gramsample of hamburger?