You put 1 ml of culture into 9 ml of broth diluent, and then you put 1 ml of that dilution into 9 ml of broth diluent, and then again you put 1 ml of the diluted culture into 9 ml of broth diluent. You inoculated an agar plate with 1 ml of the most diluted tube and 45 colonies grew overnight. What is the original bacterial density (CFU/ml) in the original undiluted culture?

Question

You put 1 ml of culture into 9 ml of broth diluent, and then you put 1 ml of that dilution into 9 ml of broth diluent, and then again you put 1 ml of the diluted culture into 9 ml of broth diluent.  You inoculated an agar plate with 1 ml of the most diluted tube and 45 colonies grew overnight.  What is the original bacterial density (CFU/ml) in the original undiluted culture?
4,500 CFU/ml
45,000 CFU/ml
450 CFU/ml
9,000 CFU/ml

GPT 3.5 · Answer

The original bacterial density (CFU/ml) in the original undiluted culture is 45,000 CFU/ml.