FIG. 3.

Western blot analysis of SEB production. (A) Western blot of total extracellular proteins of S. aureus S6 (lane 1), PC1700 (agr) (lane 2) PC1841 (sarA) (lane 3), and PC1845 (sarA agr) (lane 4). All lanes contain exoproteins from the equivalent of 0.05 OD₆₀₀ units of original culture (T = 18 h). Proteins were separated by SDS-PAGE on a 10% (wt/vol) gel, transferred onto a nitrocellulose membrane (BDH), and probed with a 1:2,000 dilution of antibodies to SEB (Sigma) prior to colorimetric detection as described in Materials and Methods. (B) The relative intensity of each protein band quantified by densitometry (mean of three experiments plus standard deviation).