FIG 1.
Cells with a wide range of σE activities can be distinguished on lactose–TTC–X-Gal agar. The activity of σE from the σE-dependent rpoHp3-lacZ reporter is shown on LB–X-Gal (left), lactose–TTC–X-Gal (center), and lactose-TTC (right) plates for the ΔompR strain with very low levels of σE activity, the wild-type (WT) strain with moderate levels of σE activity, and the ΔrseA strain with high levels of σE activity. Also shown are two mutants, isolated from stationary-phase ΔrseA cultures, that have mutations in rpoE that reduce its activity to different extents (8-fold decrease for the L10P mutation and 33-fold decrease for the R149Q mutation) (Table 1).