Schematic representations of the Group 1 (A), Group 1b (B), Group 2 (C), Group 2b (D), and Group 3 (E) structural groups showing variation in the region upstream of gapR . (A) Primer positions and important conserved sequence motifs are indicated. Identical 77 bp insertions within the semi-variable region (diagonal cross-hatch) were identified in Groups 1b and 2b. Group 2b contains an unrelated 37 bp insertion upstream of the STAR deletion site (vertical cross-hatch). Group 3 contains the STAR start signature followed by 70 bp of sequence unrelated to other STAR elements or semi-variable regions examined (horizontal cross-hatch). (F) Schematic representation of the gapR STAR element deletion site, comparing the locus from strain BB and MRSA252 and indicating the region missing from the Group 2 strains. The conserved sequences flanking the deletion site are highlighted in each strain.