FIG 7 .

Deficiency of arginine uptake and arginine metabolism regulator ArgR2 interferes with pneumococcal phagocytosis. J774A.1 murine macrophages were infected with a multiplicity of infection of 50 pneumococci of wild-type (wt) strain TIGR4 or its isogenic arcA-C, arcA-T, or argR2 mutant. (A) Viable and recovered intracellular pneumococci were determined by colony counting 30 min postinfection by applying the antibiotic protection assay. Shown are the mean values and standard deviations of three independent experiments performed in triplicate. *, P < 0.05; ***, P < 0.001. (B) Immunofluorescence microscopy of host cell-attached and intracellular pneumococci. J774A.1 murine macrophages were infected with pneumococcal strain TIGR4 or the ΔarcA-T or ΔargR2 mutant for 5, 30, or 60 min. Intracellular pneumococci were stained with Alexa 568 (red), while adherent bacteria appear yellow (Alexa 488 and Alexa 568). Bars represent 10 µm.