Fig. 5.

LytM endopeptidase is required for protein A release from the staphylococcal envelope. (A) S. aureus WT and atl, sle1, lytN, lytM, or atl/sle1/lytN mutant cultures were centrifuged. Proteins in the culture media were separated with the supernatant (marked “S”) from the bacterial pellet (marked “P”). After treatment of the staphylococcal cell wall envelope with lysostaphin, proteins in both fractions were analyzed by immunoblotting with polyclonal antibodies against protein A (αSpA) or sortase A (αSrtA). (B) Immune reactive signals from three different samples analyzed as shown in A were averaged, SEMs determined, and statistical significance analyzed with the two-tailed Student t test. Only the lytM mutant strain released less protein A than WT S. aureus (P = 0.002).