Direct measurements of gene expression. (a) Western blot of Fis at various stages of growth. Lanes 1 to 8 correspond to the times shown in b and c. The band corresponding to Fis is indicated by the arrow. A non-specific band recognized by the anti-Fis antibody (marked by an asterisk) has been used for normalization. (b) Correspondence between Western blot measurements (black squares) and GFP concentration. The dashed lines denote the 95% confidence bands. Both the reporter concentration and the Western blot values are normalized with respect to the peak in mid-exponential phase. (c) Idem for the luciferase concentration. (d) Northern blot of fis mRNA at various stages of growth. Lanes 1 to 7 correspond to the times shown in b and c. Equal amounts of total RNA were loaded in each lane. (e) Correspondence between Northern blot measurements (black squares) and GFP synthesis rate. Normalization is carried out in the same way as for the Western blot. (f) Idem for the luciferase synthesis rate.