Figure 1

Adhesion capacities of S. aureus DSM20231 and its clpC derivatives to non-professional phagocytes. (a) HaCaT and Ea.hy926 cells were challenged with the S. aureus strains DSM20231 (WT; black bars), the clpC mutant PBM001 (clpC; white bars), and the clpC complemented PBM001 derivative (clpC/clpC⁺, grey bars) at a MoI of 100, respectively, and co-cultured for 90 min. Non-adherent bacteria were subsequently removed by washing. Eukaryotic cells were afterwards lysed by sonication, and CFU rates in lysates determined by plate counting. Data are presented as mean + SD (n = 6 biological replicates). ns, not significant (Kruskal Wallis test followed by Dunn’s post-hoc test). (b–d) Single cell force spectroscopy of DSM20231 (black bars) and PBM001 (white bars) cells on Ea.hy926 cells. (b) Representative retraction force profiles obtained by recording force-distance curves in DMEM between bacteria and Ea.hy926 cells spread on glass bottom petri dishes for 24 h. (c,d) Maximum adhesion force- and rupture length histograms. Histograms are from a total of 320 curves from 5 independent cell pairs per bacterial strain. They were obtained by determining, for each curve, the force of the strongest adhesive event (c) and the distance of the last rupture event (d). ns, not significant (Mann-Whitney U test).