Fig. 2. The effect of glucose on lac operon expression is eliminated in pgi or pfkA mutants. PP6 (wild-type), KK27 (ptsG^–), KK52 (pgi^–) and KK51 (pfkA^–) cells were grown in LB medium with 1% lactose (Lac) or 0.5% glucose (Glc) + 0.5% lactose. Culture samples were taken at an OD₆₀₀ of 0.6 and β-galactosidase activities were determined.