FIG. 5.

katA expression is induced when cells are grown in LB medium lacking supplemental manganese. Cells were grown in LB medium at 37°C to an OD₆₀₀ of 0.3 to 0.5; diluted back to an OD₆₀₀ of 0.02 into fresh, prewarmed LB medium or LB medium supplemented with 100 μM MnCl₂; and then grown until 3 h after exit from exponential growth. Catalase levels were monitored by using a lacZ transcriptional fusion to katA. Filled symbols, LB medium without Mn(II); open symbols, LB medium with Mn(II). Strain SH536 (sda⁺ amyE::P_katA-lacZ) was used.