PSM-mec production in <i>S. aureus</i> and <i>S. epidermidis</i>.

<p>(A) RP-HPLC elution profile of <i>S. aureus</i> MSA3407 and <i>S. epidermidis</i> RP62A culture filtrates (at 8 h of growth). Equal volumes were applied to a C8 column and eluted with a 0.1% TFA water/acetonitrile gradient. PSM peptides characteristically elute at very high acetonitrile concentrations. Peaks of major PSM peptides and the newly identified PSM-mec are indicated. (B) Electrospray ion chromatogram of the PSM-mec peak obtained by RP/HPLC/ESI-MS (<i>S. epidermidis</i> RP62A). The respective PSM-mec ESI chromatogram of <i>S. aureus</i> MSA3407 or any strain with PSM-mec production showed the same m/z peaks. The series of peaks with slightly higher masses close to m/z 1208.3 are due to water and sodium adducts.