Fig. 4. FAK-deficient cells do not support S. aureus invasion. (A) Internalisation of S. aureus or S. carnosus by FAK-re-expressing fibroblasts was measured at the indicated times following infection by gentamicin/lysostaphin protection assays. Values are means±s.d. of two independent experiments done in triplicate. (B) FAK-re-expressing [FAK(+)] or FAK-deficient [FAK(–)] mouse fibroblasts were infected with S. aureus for 2 hours and employed in gentamicin/lysostaphin protection assays. Values are means±s.d. of three independent experiments done in triplicate (C) FAK(+) or FAK(–) fibroblasts were infected with FITC- and biotin-labelled S. aureus for 2 hours. After fixation, extracellular bacteria were detected by addition of streptavidin-Cy5. Extracellular bacteria (arrowheads) stain positive with both FITC and Cy5, whereas intracellular bacteria (arrows) are labelled with FITC only. Bars, 10 µm. (D) FAK(–) and FAK(+) cells were infected for 1 hour with S. aureus and analysed by scanning electron microscopy. Pseudocoloured images depict bacteria in red and the fibroblast surface in green.