Figure 1.

The enterobactin (Ent) biosynthetic pathway is a prominent contributor to the iron-responsive uropathogenic Escherichia coli UTI89 exometabolome. Sparse principal component analysis (sPCA) was performed to identify LC–MS exometabolome profiles that distinguish four groups of conditioned media: UTI89 grown in low and high iron (addition of 100 μM FeCl₃) media (wildtype and wildtype + Fe, respectively) and the Ent-null mutant UTI89ΔentB grown in low and high iron media (entB and entB + Fe, respectively). A, the score plot depicts each replicate LC–MS exometabolome (as a data point) as a function of principal components 1 and 2 (PC1, PC2), which are the first and second most influential modes of exometabolomic variation across all specimens. The combination of exometabolites comprising the PC1 axis separate the wildtype, low iron condition from the other conditions. B, LC–MS/MS chromatograms corresponding to the precursor–product ions from Ent (m/z 668.0) for each experimental group. Chromatograms are displayed in identical ion current unit scales. C, a PC1 loading plot displays the contribution of each LC–MS exometabolite feature to the PC1 value. The 13 most influential metabolites with greater abundance in wildtype UTI89 (lower PC1 value) are identified as red data points.