FIG. 7.

Extracellular and intracellular growth of wild-type and mutant strains of F. tularensis LVS and F. novicida U112. For extracellular growth (A and B), bacteria were grown in both iron-replete (filled symbols) and iron-restricted (open symbols) media. The wild-type F. tularensis LVS strain (panel A, circles), its figA mutant (A, triangles), the wild-type F. novicida strain (B, circles), and its figA mutant (B, triangles) were grown as described in Materials and Methods. To assess intracellular growth (C and D), these same strains were grown in the macrophage cell line J774A.1 as described in Materials and Methods. (C) Wild-type F. tularensis LVS (filled columns) and its figA mutant (open columns). (D) Wild-type F. novicida (filled columns) and its figA mutant (open columns). These data are the means from two independent experiments. In panel D, the difference between the F. novicida wild-type and mutant strains was significant only at 24 h postinfection (asterisk; P = 0.0096, Student's t test).