Fig. 1. S. aureus internalisation requires host cell actin dynamics. (A) 293 cells were infected with S. aureus or S. carnosus at a MOI 20 for 2 hours in the presence of the indicated concentrations of latrunculin, cytochalasin D, or jasplakinolide. Living intracellular bacteria were counted by gentamicin/lysostaphin protection assays. Values are means±s.d. of three independent experiments done in triplicate. (B) 293 cells were transfected with GFP-actin and infected with rhodamine-labelled S. aureus. Using time-lapse microscopy, the dynamics of GFP-actin in the transfected 293 cells 30 minutes after infection were recorded. Invasive bacteria induced transient local accumulation of polymerised actin (arrows). In some cases, massive actin-filled membrane protrusions wrapped around invasive bacteria (arrowheads). Elapsed time, in seconds, from the beginning of the recording is indicated.