Rns–dependent transcription start sites of fimbrial promoters. The transcription start sites of CS17, CS19, and PCFO71 fimbrial promoters were mapped by primer extension of RNA isolated from rns+ and rns::kan strains. The first nucleotide of each mRNA is underlined and wavy arrows indicate the direction of transcription. Putative–10 hexamers are shown in boxes. Lanes labeled GA and TC contain Maxam–Gilbert sequencing ladders. These are excision reactions and are therefore offset from the primer extension products by -1 nucleotide. RNA was isolated after cultures reached an optical absorbance of 1.0 at 595 nm.