Fig. 3

Phosphatidylserine externalization in BME26 cells exposed to either viable or thermo-inactivated R. rickettsii. Noninfected BME26 cells (control) or cells exposed for 48 h to either viable or thermo-inactivated R. rickettsii were treated with 400 nM staurosporine. After 6 h, cells were labeled with propidium iodide (red), annexin-V (green) and Hoechst (blue), and observed under a fluorescence microscope. a The panel at the top represents the three conditions at 40× magnification. The square areas outlined with broken lines are those areas presented in the images below the top panel, for better visualization. The light-blue arrows indicate annexin-V staining. Bar: 40 μm. b The graph represents the number of cells labeled with each probe in three independent images of each of the three biological replicates. Error bars: ± standard deviation. Asterisk indicates significant difference at *P < 0.001 (Student’s t-test)