Evolution and phylogeny of non-O157 enterohemorrhagic Escherichia coli

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Enterohemorrhagic E. coli (EHEC) are characterized by producing Shiga toxins. They can cause watery and bloody diarrhea and Hemolytic Uremic Syndrome. Within the EHEC group there is a broad spectrum of different non-O157 serotypes in addition to O157:H7. Among them are the two most important non-O157 variants O26:H11 and O91:H14/H21, whose evolution we plan to investigate in this project. Using multilocus sequencing typing, we have already demonstrated the notable diversity within these non-O157 serotypes. We postulate that characterization and analysis of core genome SNPs collected from whole-genome sequencing, coupled with epidemiological and virulence data, will provide a detailed, serogroup-specific phylogenetic topology of the emergence and spread of EHEC O26 and O91. To test this hypothesis, the following working program is proposed: 1. determination of the core genome using WG-shotgun sequencing and comparison of all previously published E. coli genomes, as well as determination of the serotype-specific core genome comparing only O26 or O91 strains, 2. SNP discovery using shotgun reads of strains spanning the geographical and temporal extremes of the population, 3. SNP analysis of our O26 and O91 strain collections to determine the serotype-specific evolutionary scenario, and 4. correlation of the pathogenicity make-up and phylogeny. In summary, we expect not only new knowledge about the evolution of the most important non-O157 serotypes but also the establishment of a new concept of serotype-specific phylogeny.