FIG 1.

Clinical UPEC isolate HM7 encodes a single siderophore. (A) Models of siderophores, siderophore uptake receptors, and heme receptors in UPEC. “UPEC” indicates all known systems that have been found in UPEC, while “CFT073” and “HM7” illustrate the systems in each of these indicated strains. (B) Number of iron acquisition systems present in a cohort of 457 UPEC strains on the bioinformatics resource PATRIC. The five systems are composed of heme uptake (ChuA or Hma) and four siderophores (enterobactin, salmochelin, aerobactin, and yersiniabactin). Presence was determined by ≥80% protein identity and coverage of select genes for each system: heme uptake (chuA or hma), enterobactin (entB), salmochelin (iroB), aerobactin (iucA), and yersiniabactin (irp1). Sequence was used from strain CFT073 for all genes, with the exception of irp1, where strain 536 was used. Genes selected for siderophores are all involved in biosynthesis. Eleven percent of strains have five systems, 48% of strains have four, 21% of strains have three, 12% of strains have two, and 8% of strains have one. (C) The prevalence of each iron acquisition system within each subdivided group. (D) Siderophore production assayed through growth on CAS agar. Five microliters of overnight LB cultures was spotted onto CAS agar, and the cultures were grown overnight at 37°C. A change from blue to orange indicates siderophore activity. White arrows indicate the colonies in all three strains, and the orange halos in the WT and complemented strains are due to diffusion of secreted siderophore.