Evolution and phylogeny of non-O157 enterohemorrhagic Escherichia coli

肠出血性大肠杆菌(EHEC)的特征是产生志贺毒素。它们会导致水样和血性腹泻和溶血性尿毒症综合征。在EHEC组中，除了O157：H7外，还有广泛的不同非O157血清型。其中有两个最重要的非O157变异体O26：H11和O91：H14/H21，我们计划在这个项目中研究它们的进化。利用多位点测序分型，我们已经证明了这些非O157血清型的显著多样性。我们推测，从全基因组测序中收集的核心基因组SNPs的特征和分析，结合流行病学和毒力数据，将为EHEC O26和O91的出现和传播提供详细的、血清群特异性的系统发生拓扑结构。为了验证这一假设，提出了以下工作程序：1.使用WG-Shotgan测序确定核心基因组并比较所有以前发表的大肠杆菌基因组，以及确定仅比较O26或O91菌株的血清特异性核心基因组；2.使用鸟枪读取跨越种群地理和时间极端的菌株来发现SNP；3.对我们的O26和O91菌株集合进行SNP分析，以确定特定于血清类型的进化情景；以及4.病原性组成和系统发育的相关性。综上所述，我们不仅期望对最重要的非O157血清型的进化有新的了解，而且希望建立一个新的血清型特异性系统发生学概念。

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.