Fig 2. Constitutive expression of the skin^Cd gene CD1231.

A: promoter region of the CD1231 gene. The mapped transcriptional start sites (+1, red) [34] and the -10 and -35 promoter elements (green boxes) that match the consensus for σ^A recognition are indicated. Also represented are the stop codon of CD1232 and the start codon of CD1231 (red). Inverted repeats upstream (grey arrows) and downstream (brown) of the +1 position are indicated as well as a possible RBS overlapping the left arm of these repeats. B: qRT-PCR analysis of CD1231 transcription in strain 630Δerm, and in sigE or spoIIID mutant. RNA was extracted from cells collected 14 h (sigE mutant) or 15 h (spoIIID mutant) after inoculation in liquid SM. Expression is represented as the fold ratio between the indicated mutants and the wild-type (WT). Values are the average ± SD of two independent experiments. C: cells of the C. difficile 630Δerm strain carrying a P_CD1231-SNAP^Cd transcriptional fusion were collected after 24 h of growth in liquid SM, stained with TMR-Star and the membrane dye MTG, and examined by phase contrast (PC) and fluorescence microscopy. The merged images show the overlap between the TMR-Star (red) and MTG (green) channels. The yellow arrow shows a vegetative cell expressing P_CD1231-SNAP^Cd, the white arrow shows expression in the forespore and the red arrow expression in the mother cell. Scale bar, 1 μm.