FIGURE 2: Beta-galactosidase assays of aphA expression from the promoter P2 during carbon starvation in various mutant strains of E. coli. Time zero indicates the time right before the downshift of cells from the MOPS complete medium to the same medium without glucose. The Miller units were normalized to that of wild type strain at time zero, i.e., before downshift. Three biological replicates were performed, and the average and standard deviations are shown. The significance of unpaired t-test is indicated by the symbol * (p-value < 0.05).