FIG. 6.
β-Galactosidase activities during growth in different sugars. (A) β-Galactosidase activities of D39 and BgaAC (GK315) in increasing glucose. (B) β-Galactosidase activities of ccpA deletion mutants of D39 (GK220) and BgaAC (GK320). For both panels A and B, strains were grown to mid-exponential growth phase in D medium supplemented with 0.1% glucose and then diluted 1/12 in D medium supplemented with the indicated glucose concentration. β-Galactosidase assays were performed with mid-exponential phase cultures. The results are the means (plus standard errors) of three replicates. (C) β-Galactosidase activities in various PTS sugars. Strains were grown to mid-exponential growth phase in D medium with the indicated sugar (0.1%) and then diluted 1/12 in D medium containing the same sugar. For the no-sugar culture, strains were first grown in D medium containing 0.1% glucose and then diluted 1/12 into D medium lacking a sugar. When either no sugar or galactitol was added to the growth medium, very little growth was observed for either D39 or the BgaAC mutant. For these cultures, β-galactosidase assays were performed after growth ceased (after glucose was exhausted for the no-sugar culture). For all others, β-galactosidase was determined at mid-exponential phase. The results are the means (plus standard errors) of three replicates. *, P < 0.05 compared to D39 grown in glucose. **, P < 0.05 compared to BgaAC grown in glucose.