Transcription, promoters and cis -regulatory motifs within the nrd operons. (A), (B), and (C) correspond to the nrdRJ (PPA1025-1026), nrdAB (PPA2121-2122), and nrdDG (PPA2137-2136) operons, respectively. For each panel, the tracks show, from top to bottom, the positions of annotated genes, the position of TSSs (Additional file 3) and the gRNA-seq data. As the nrdDG operon is encoded on the reverse strand, the corresponding RNA-seq data is depicted by red negative bars. The inset in each panel shows the positions of predicted nrd-boxes and their sequences (underlined text) in relation to the TSS (bold, larger font text), where appropriate. The remainder of the labelling is as Figure 2.