Draft

In the viable counts portion of this lab we used viable counts to observe the number of cells

present on Petri dishes inoculated with decreasing dilutions of E. coli. The E. coli were diluted in

sterile saline and spread at dilutions of 10-1, 10-2, 10-3, 10-4, 10-5, 10-6, 10-7, and 10-8. Dilution and

viable counts is a useful technique because it allows live cells to be counted, eliminating the

variable of dead cells contributing to a cell count. Colony forming units per ml (CFU/ml) were

calculated to determine the number of cells growing at each dilution. I expected the highest

CFU/ml would be from dilutions containing a higher concentration of cells, and the lowest from

the more dilute samples. . I expected that as the solutions increased in dilution, , the CFU/ml

would decrease due to less E. coli being transferred and inoculated onto the Petri dish.