Fig. 4: Susceptibility of S. aureus mutants to cell wall agents and alterations in cell surface charge.
a, e Sensitivity of S. aureus mutants to Triton X-100. Triton X-100 (0.1–1%) was added to PBS-washed cell suspensions and turbidity monitored at OD600 nm. Results represent the mean (n = 3) with standard deviation indicated by shading. b Sensitivity of S. aureus mutants to lysostaphin. Lysostaphin (2.5 µg/ml) was added to PBS-washed cell suspensions and turbidity monitored at OD600 nm. Results represent the mean (n = 3) with standard deviation indicated by shading. c, h Changes in bacterial surface charge in a cytochrome c binding assay. Cytochrome c (5 mg/ml) was added to concentrated cells and the supernatant following centrifugation to pellet cells measured at A440 nm (n = 3). d, i D-Ala content of S. aureus cells determined by HPLC analysis. Results represent the mean (n = 3) with standard deviation. f, g Susceptibility of S. aureus fmtA and vraF mutants to EDTA and DTPMP. Growth in the presence of each chelator was measured at OD600 nm and normalised against controls without treatment to give the percentage growth. Results represent the mean and standard deviation of an independent experiment performed in triplicate. An additional biological repeat of each treatment produced similar results (Fig. S11a,b). One-way ANOVA analysis with a post hoc Dunnett test was used to compare mutant strains to the WT; *p < 0.05, **p < 0.01, ***p < 0.001 and ****p < 0.0001.
