Journal Article

Comparative genomics of enterohemorrhagic Escherichia coli O145:H28 demonstrates a common evolutionary lineage with Escherichia coli O157:H7

Cooper, Kerry K, Carter, Michelle Qiu, Parker, Craig T, Korlach, Jonas, Clark, Tyson A, Huynh, Steven, Mandrell, Robert E, Louie, Jacqueline W, Ahmed, Sanaa, Chain, Patrick S

2014

Overview

Background Although serotype O157:H7 is the predominant enterohemorrhagic Escherichia coli (EHEC), outbreaks of non-O157 EHEC that cause severe foodborne illness, including hemolytic uremic syndrome have increased worldwide. In fact, non-O157 serotypes are now estimated to cause over half of all the Shiga toxin-producing Escherichia coli (STEC) cases, and outbreaks of non-O157 EHEC infections are frequently associated with serotypes O26, O45, O103, O111, O121, and O145. Currently, there are no complete genomes for O145 in public databases. Results We determined the complete genome sequences of two O145 strains (EcO145), one linked to a US lettuce-associated outbreak (RM13514) and one to a Belgium ice-cream-associated outbreak (RM13516). Both strains contain one chromosome and two large plasmids, with genome sizes of 5,737,294 bp for RM13514 and 5,559,008 bp for RM13516. Comparative analysis of the two EcO145 genomes revealed a large core (5,173 genes) and a considerable amount of strain-specific genes. Additionally, the two EcO145 genomes display distinct chromosomal architecture, virulence gene profile, phylogenetic origin of Stx2a prophage, and methylation profile (methylome). Comparative analysis of EcO145 genomes to other completely sequenced STEC and other E. coli and Shigella genomes revealed that, unlike any other known non-O157 EHEC strain, EcO145 ascended from a common lineage with EcO157/EcO55. This evolutionary relationship was further supported by the pangenome analysis of the 10 EHEC str ains. Of the 4,192 EHEC core genes, EcO145 shares more genes with EcO157 than with the any other non-O157 EHEC strains. Conclusions Our data provide evidence that EcO145 and EcO157 evolved from a common lineage, but ultimately each serotype evolves via a lineage-independent nature to EHEC by acquisition of the core set of EHEC virulence factors, including the genes encoding Shiga toxin and the large virulence plasmid. The large variation between the two EcO145 genomes suggests a distinctive evolutionary path between the two outbreak strains. The distinct methylome between the two EcO145 strains is likely due to the presence of a Bsu BI/ Pst I methyltransferase gene cassette in the Stx2a prophage of the strain RM13514, suggesting a role of horizontal gene transfer-mediated epigenetic alteration in the evolution of individual EHEC strains.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,Springer
• Subject: Analysis / Animal Genetics and Genomics / Bacteriology / BASIC BIOLOGICAL SCIENCES / Biological Evolution / Biomedical and Life Sciences / Biotechnology & Applied Microbiology / Comparative genomics / DNA methylation / E coli / Enterohemorrhagic Escherichia coli / Enterohemorrhagic Escherichia coli - classification / Enterohemorrhagic Escherichia coli - genetics / Enterohemorrhagic Escherichia coli - virology / Escherichia coli / Escherichia coli - classification / Escherichia coli - genetics / Escherichia coli - virology / Escherichia coli O157 - classification / Escherichia coli O157 - genetics / Escherichia coli O157 - virology / Escherichia coli Proteins - genetics / Escherichia coli Proteins - metabolism / Foodborne diseases / Genes / Genetic aspects / Genetics & Heredity / Genome, Bacterial / Genomics / Health aspects / Infections / Life Sciences / Methylation / Methyltransferases - genetics / Methyltransferases - metabolism / Microarrays / Microbial Genetics and Genomics / O145 / Outbreaks / Phylogeny / Physiological aspects / Plant Genetics and Genomics / Plasmids / Prokaryote microbial genomics / Prophages - metabolism / Proteomics / Research Article / Serotyping / Shiga Toxin - genetics / Shiga toxin-producing Escherichia coli / Shigella / Shigella - classification / Shigella - genetics / Toxins / Virulence (Microbiology) / Virulence Factors - genetics