Figure 3. Each point represents mass spectrometry (MS)-based measurement of the levels of 6-P-F-Asp in one biological replicate.

Samples were prepared using the cell pellet from a 1.3-ml culture of Salmonella wild-type (14028) or ΔfraB::kan (HMB206) or Δfra island deletion (HMB215) mutant. Two transitions were measured to confirm quantitation; data from one transition (Table S4B) are shown here, while data from a second transition (Table S4A) are shown in Fig. S3. The values provided are the mean ± standard deviation from three biological replicates. The values for wild-type and Δfra island deletion are very low and below 20 nmol, the lowest concentration used for establishing the standard curve; however, they are provided here to indicate the reproducible absence of 6-P-F-Asp in these two strains.