one ml of a water sample was pipetted into a 9 ml dilution blank. one-tenth (0.1) ml of this solution was pipetted into a 9.9 ml dilution blank. from this dilution, one-tenth (0.1) ml was plated with 25 ml of culture medium. after incubation, 220 colonies arose. how many colony-forming units (cfus) were present per ml of the original culture? (3 pts).
