Fig. 2.

Arginine is required for mutant multiplication in macrophages. Amino acid supplementation. J774.1 cells were infected with wild-type F. novicida (WT) or ΔargP mutant for 24 h, in medium supplemented (+AA) or not, with a pool of essential E-AA amino acids, A, or NE-AA, B, each at a final concentration of 1.5 mm. C, Arginine supplementation. J774.1 cells were infected with wild-type F. novicida (WT), or ΔargP mutant for 24 h with medium, supplemented (+AA) or not, with arginine 1.5 mm (+ Arg). D, Arginine transport assay. Kinetics of uptake of ¹⁴C radiolabeled arginine by wild-type F. novicida (WT, open circles) and ΔargP mutant (ΔargP, closed triangles), at substrate concentrations ranging from 1 to 50 μm. Ordinate, picomoles (pmol) of arginine taken up per minute (per sample of app. 2.5 × 10⁹ bacteria). Abcissa, final concentration of arginine tested.