esxA in S. aureus. A. Schematic representation of the ess locus of S. aureus Newman (GenBank accession no. NC_009641). ORF notations correspond to those used by Anderson et al. . The σA promoter, transcriptional start point (TSP) and ribosomal binding site (RBS) as well as the start codon of esxA are indicated. B. Northern blot of esxA of strain Newman and the isogenic ΔesxA mutant (BS304) during growth. The ethidium bromide-stained 16S rRNA pattern is shown as an indication of RNA loading. C. Primer extension analysis of esxA. Lanes C, T, A and G show the dideoxy-terminator sequencing ladder and lane RT the reverse transcription product obtained using primer pe_esxA_2. The TSP is marked by an arrow. The same TSP was identified using primer pe_esxA_1 (data not shown).