Figure 7.

Interaction of S. aureus USA 300 LAC with histone H3. A, microtiter wells coated with histone H3 were incubated with cells of the indicated bacteria. Wells were washed with PBS, fixed with formaldehyde, and stained with crystal violet, and the absorbance at 595 nm was measured in an ELISA plate reader. Means and S.D. of results of two independent experiments, each performed in triplicate, are presented. Statistically significant differences is indicated (Student's t test; *, p < 0.05). B, S. aureus strain USA 300 LAC, the double mutant ΔfnbAfnbB, or the mutant overexpressing FnBPB or FnBPA was incubated with histone H3. After several washings, proteins bound to the cell surface were released by extraction buffer, separated by SDS-PAGE under nonreducing conditions, and transferred to a nitrocellulose membrane. The membrane was sequentially probed with rabbit anti-histone IgG and HRP-conjugated goat anti-rabbit IgG. The figure is representative of two independent experiments. C, densitometric analysis of histone H3 binding to S. aureus LAC and its mutants as reported in B. The band intensity was quantified relative to a sample of pure histone H3 (5 μg, 100 intensity). The reported data are the mean values ± S.D. from two independent experiments. Statistically significant differences are indicated (Student's t test; *, p < 0.05).