FIGURE 2.

Francisella catalase is necessary to maintain calcium homeostasis following infection. Murine alveolar macrophages (MHS cell line) were infected with LVS or ΔkatG for 1 h. Macrophages were loaded with Fura Red, whose fluorescence is inhibited by calcium, lifted, and analyzed on ImageStream flow cytometer. A depicts the mean Fura Red fluorescence. B depicts representative images from the mean. C depicts screening of multiple LVS mutants was accomplished by the analysis of Fura Red fluorescence with a plate reader. 300 μm H₂O₂ was used as a control for calcium influx. The data represent the mean fluorescence intensity values ± S.E. of three independent experiments. **, p < 0.001; #, p < 0.00001.