FIG 7.

Replacing the SpA sorting signal with the sorting signal from SdrE reduces release of SpA by LAC*. (A) Protein A on the surface of LAC* sbi, LAC* sbi [SpAΩSdrESS], and LAC* sbi lytM [SpAΩSdrESS] was detected using FITC-labeled rabbit IgG, and the fluorescence intensity was measured using flow cytometry. Values are expressed as a percentage of the mean fluorescence intensity measured for LAC* sbi grown to an OD₆₀₀ of 0.3. Bars represent the mean values, and error bars indicate the standard errors of the means of three independent experiments. (B) Protein A was captured from culture supernatants using chicken anti-SpA polyclonal IgY and detected using biotin-conjugated mouse monoclonal anti-SpA IgG followed by streptavidin-HRP in an ELISA. The absorbance at 450 nm was measured, and the mean reading from wells incubated with culture supernatants from LAC* spa sbi were subtracted from the readings for all other wells to account for background. Values are expressed as a percentage of total released SpA measured for LAC* sbi grown to an OD₆₀₀ of 0.3. Bars represent the mean of four independent experiments. Error bars represent the standard errors of the means. **, P = 0.007; ***, P < 0.0001; ns, not significant (P > 0.05).