Fitness Islands in Uropathogenic Escherichia coli

The size of sequenced Escherichia coli genomes varies from 4.6 Mb for the fecal/commensal E. coli K-12 strain MG1655 to 5.5 Mb for enterohemorrhagic E. coli (EHEC) strain O157:H7 EDL933. The majority of these differences are attributed to the insertion of large regions of genomic DNA. This chapter examines genes present on genomic islands and islets of uropathogenic E. coli (UPEC), with a primary focus on genes contributing to the overall fitness of the organism rather than traditional virulence genes. The acquisition and stable integration of multiple genomic islands and islets encoding fimbrial adhesins in UPEC illustrate the significance of adhesion within the urinary tract. The abundance of horizontally acquired, coregulated fimbrial adhesins in UPEC, each with distinct adhesive moieties, demonstrates a clear functional redundancy. The authors identified the sit iron transport system in six of seven arbitrarily selected UPEC strains and only one of three fecal/commensal strains (not in E. coli K-12) using CGH. Several well-studied E. coli strains, ABU strain 83972 and E. coli Nissle 1917, may hold the key to understanding their pathogenic E. coli relatives. ABU strain 83972 has lost many of the typical UPEC virulence genes and yet has retained systems contributing to fitness, particularly those involved in iron acquisition and transport (aerobactin, salmochelin, yersiniabactin, heme/hemoglobin, and sitABCD).