Figure 1. Transcriptional organization of the sil locus as previously deduced.

sil is known to contain three polycistronic transcriptional units: silA/B encoding the TCS SilA-SilB, silE/D/CR encoding the ABC transporter system (SilD/E), plus the signaling peptide SilCR, and blp encoding the bacteriocin-like peptides BlpM, spy_0484 and spy_0486. The transcription of the above-mentioned units is initiated from P₁, P₃, and P₄ promoters, respectively. The monocistronic transcript of silC is initiated from the P₂ promoter. Promoters induced and non-induced by SilCR are illustrated by filled and empty flags, respectively. Arrows indicate genes; waved-dotted lines represent transcripts; TT stands for a transcriptional terminator.