FIG. 3.

(A) Growth of the C. jejuni wild type and sdaA mutant in MEM-α, in the presence and absence of an added carbon source. Solid bars (c), no added carbon source; open bars (pyr), 20 mM sodium pyruvate; and hatched bars (ser), 20 mM l-serine. Strains were pregrown overnight in BHI-FCS, harvested, washed, and resuspended in MEM-α before being inoculated into prewarmed MEM-α. It should be noted that, in MEM-α alone (solid bars), a basal level of growth occurs owing to the presence of amino acids in the medium (starting optical density at 600 nm [OD _{600 nm}] was 0.28). The data represent the mean of two separate experiments ± standard deviation. (B and C) Analysis of l-serine utilization by C. jejuni wild-type (B) and sdaA mutant (C) strains conducted by using proton NMR spectroscopy. Cells were grown with 20 mM l-serine in MEM-α. Culture supernatants for each strain were collected before (T₀) and after 24 h (T₂₄) of inoculation. The serine proton resonances at a chemical shift of 3.7 to 3.9 ppm are indicated with arrows, as determined from the spectrum for MEM-α alone. The chemical shift reference used was 1 mM trimethylsilylpropionate (0 ppm), which was included in all the samples. The identity of the resonance at 1.2 ppm in the sdaA samples was not determined.