FIG. 6.

Quantitative extracellular murein hydrolase assays of S. aureus strains with or without an intact rsbU gene. Aliquots of 100 μg of extracellular proteins isolated from 16-h cultures of 8325-4 (rsbU-negative; open circles), SH1000 (rsbU⁺; closed circles), IK184 (ΔrsbUVWsigB; open triangles), and Newman (rsbUVWsigB⁺; closed triangles) were each added to a 1.0-mg/ml suspension of M. luteus cells, and the murein hydrolase activity of each sample was measured as a decrease in turbidity over a 4-h time course experiment. These data are the average of three independent experiments. The error bars on the graph correspond to the standard errors of the means.