Supplemental Experimental Procedures Bacterial Strains and Reagents

isolate from a patient with NF and STSS [S1], GAS M49 strain NZ131 [S2], and L. lactis strain NZ9000 [S3] were propagated via Todd-Hewitt broth (THB) or agar (THA) (Hardy Diagnostics). Escher-ichia coli TOP10 (Invitrogen) were grown on Luria-Bertani media (LB). For selection, erythromycin was used at 5 mg/ml (GAS and L. lactis) or 500 mg/ml (E. coli) and chloramphenicol at 2.5 mg/ml (GAS and L. lactis) and 20 mg/ml (E. coli). Genomic DNA preparation was performed with the MoBio Genomic DNA kit. GAS and L. lactis were made competent for transformation by electroporation by growth in THB + 0.6 % glycine as described [S4]. Unless indicated, bacteria were grown to logarithmic phase (OD600 = 0.4) and resus-pended in PBS or tissue culture media to the desired concentration. Targeted Mutagenesis and Expression Cloning Via precise, in-frame allelic replacement, the sda1 gene from GAS M1 strain 5448 was removed and replaced with the chloramphenico