Promoter activities of acrA and acrD from Erwinia amylovora. The activity was determined in the course of growth in LB broth, OD600, optical density at 600 nm. (A) Relative mRNA transcript abundance of acrA and acrD during cellular growth of Ea1189 as determined by quantitative RT-PCR. The relative mRNA level was related to the highest average value determined for a gene, which was defined as 100%. (B) Expression of acrA and acrD as determined by transcriptional fusions with the reporter gene egfp. E. amylovora wild type was transformed with pBBR.acrA-Pro.egfp and pBBR.acrD-Pro.egfp, respectively. Experiments were performed in triplicates with similar results.