Figure 7

The germination state of spores influences the viability of B. anthracis -infected cells. RAW264.7 cells were incubated for 30 min with B. anthracis spores (MOI 10) in DMEM in the presence (+, black bars) or absence (-, white bars) of FBS (10%). After 30 min, the cells were washed to remove extracellular B. anthracis, and then further incubated with FBS (10%) and, as described under "Methods," with gentamicin to germinate and kill any remaining spores that had not been germinated. After 15 min, the cells were washed and then further incubated in the absence of gentamicin. At 0 (immediately after gentamicin removal), 60, or 240 min after removal of gentamicin, as indicated, the cells were evaluated for mammalian cell death via PI uptake, as described under Materials and Methods. The data are rendered as the fold-increase of PI uptake relative to non-infected cells in the absence or presence of FBS at 5, 60, or 240 min, as indicated. The rendered data have been combined from three independent experiments, each conducted in triplicate. Error bars indicate standard deviations. The P values were calculated to evaluate the statistical significance of the differences between the fold-increase of PI uptake between cells incubated with spores in the absence or presence of FBS.