FIG. 1.

(A and B) Growth in minimal medium limited in iron and manganese. The OD₆₀₀ after 17 h of culture at 37°C and 220 rpm in the presence of various amounts of iron (A) and manganese (B) are indicated (initial OD₆₀₀, 0.05). (C and D) Divalent metal ion uptake as determined by a quick-filtration assay with a liquid scintillation counter. Bacteria were incubated in uptake medium for 6 min after addition of metals, including the radiotracers ⁵⁴Mn (C) and ⁵⁵Fe (D). The means ± standard errors of the means for three (A and B) or two (C and D) independent experiments are shown. Active transport was indicated by the difference in metal uptake measured at 4 and 37°C. W, wild-type S. enterica serovar Typhimurium; M, mntH mutant; S, sitABCD mutant; F, feoB mutant; MS, mntH sitABCD mutant; MF, mntH feoB mutant; SF, sitABCD feoB mutant; MSF, mntH sitABCD feoB mutant; OD1, optical density unit. Pairwise Student's t tests were performed to determine whether the difference observed between a mutant and the wild type is significant. One asterisk indicates that the P value is <0.05, and two asterisks indicate that the P value is <0.01.