Control 1

The absence of transformants from the 100-200 million plated control E. coli (table 2), suggests that the background resistance to ampicillin is below one in 100-200 million. While the number of cells plated on each amp⁺ plate extends up to several billion (see experiment results), the background resistance is too low to have a significant effect over other errors. Therefore, for all amp⁺ plates, the number of CFU’s equals the number of transformants at the manipulated pH. This was assumed in all calculations, since the same stock of E. coli was used in all three experiments.