FIG 3.

Visualization of the phoZ reporter activity under the control of the hpdBCA promoter and a constitutive fdx promoter. Strains 630Δerm phpdBCA-phoZ (A) and 630Δerm P_fdx-phoZ (B) were grown for 4 h in MM, in MM supplemented with 2 mg/ml p-HPA, or in MM supplemented with 0.4 mg/ml tyrosine. The expression of the phoZ reporters was quantified by using the following formula: [OD₄₂₀ – (OD₅₅₀ × 1.75)] × 1,000/t (min) × OD₅₉₀ × volume of cells (ml). The data represent means and standard errors from three biological replicates. Statistical analyses were undertaken using linear regression to determine whether there is a significant effect on growth medium composition in 630Δerm P_hpdB-phoZ (A) and 630Δerm P_fdx-phoZ (B) strains (**, P < 0.01).