Physical map of the lytSR operon of S. epidermidis 1457 and construction of lytSR knockout mutant. Arrows depict open reading frames and indicate their orientations. lytSR operon were replaced with the erythromycin resistance gene (ermB) as indicated. The ermB gene and chromosomal regions flanking the corresponding deletions were amplified by PCR and cloned into plasmid pBT2, yielding the integration vectors pBT2-ΔlytSR. The crosses indicate the sites of homologous recombination.