Figure 2. Escherichelin production is iron repressible and dependent on early Ybt biosynthetic enzymes.

Escherichelin levels in culture supernatants were quantified by LC-MS/MS relative to a ¹³C-IS. (A) UTI89 grown in complete M63 medium with or without 16.2 mg/l FeCl₃ (34). Data represent the mean of 3 replicates, with SD plotted. ***P < 0.001, by unpaired t test. (B) Schematic of the Ybt biosynthetic pathway. Black zig-zag line designates a phosphopantetheine group covalently attached to the biosynthetic enzyme. Green designates chemical moieties built by early biosynthetic enzymes (YbtS, YbtE, and HMWP2), and blue designates chemical moieties built by late biosynthetic enzymes (HMWP1 and YbtU). (C) Isogenic mutants of UTI89 in select genes of the Yersinia HPI grown in iron-restricted medium. Data represent the mean of 8 replicates, with SD plotted.