Uptake of B. anthracis spores into mammalian cells cultured under germinating or non-germinating conditions. RAW264.7 cells (A, D), MH-S cells (B, E), or JAWSII cells (C, F) were incubated with B. anthracis spores (MOI 10) in DMEM, RPMI, or DMEM, respectively, in the presence (+, black bars) or absence (-, white bars) of FBS (10%), and then evaluated at 5 or 60 min by flow cytometry and in the presence of trypan blue (0.5%) for the percentage of cells with intracellular spores (A-C), and, for total cell associated spore fluorescence (D-F), as described under Materials and Methods. (A-C) The data are rendered as the percentage of infected cells with the entire population that has internalized spores. (D-F) The data are expressed as the change in MFI, normalized to cells at 5 min post infection in FBS-free medium. To generate the bar graphs, data were 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 in percent infected cells (A) or total intracellular spores (B) between cells incubated in the absence or presence of FBS.