Location: Produce Safety and Microbiology ResearchTitle: Complete genome sequences of two atypical enteropathogenic Escherichia coli O145 environmental strains
Submitted to: Genome Announcements
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2018
Publication Date: 5/10/2018
Citation: Carter, M.Q., Pham, A.C. 2018. Complete genome sequences of two atypical enteropathogenic Escherichia coli O145 environmental strains. Genome Announcements. 6:e00418-18. https://doi.org/10.1128/genomeA.00418-18.
Interpretive Summary: Evolution of Shiga toxin-producing Escherichia coli (STEC) has been postulated as a model of stepwise acquisition and/or loss of virulence and phenotypic traits. We previously showed that STEC O145:H28 shares a common evolutionary lineage with STEC O157/EPEC (enteropathogenic E. coli) O55 and belongs to phylogroup E. A recent study reported that STEC O145:H25 is genetically more similar to other non-O157 STEC strains of phylogroup B1 than to O145:H28, suggesting a parallel evolution of STEC O145. E. coli O145:H34 strains RM14715 and RM14723, both isolated from a leafy green-growing region in Yuma, Arizona, exhibit a distinct genotype compared with the STEC O145:H28 outbreak and environmental strains. To better understand the diversity of E. coli O145, we sequenced the genomes of RM14715 and RM14723. The genome of RM14715 is composed of a 4,825,089-bp chromosome, encoding 4,947 CDSs, 22 rRNA, and 88 tRNAs. The genome of RM14723 genome is composed of a 4,754,025-bp chromosome, encoding 4,826 CDSs, 22 rRNA, and 88 tRNAs. A total of 4,369 CDSs are conserved between the two genomes; while 578 and 457 CDSs are specific to RM14715 and RM14723, respectively. Unlike either STEC O145:H28 or O145:H25, both O145:H34 strains belong to phylogroup B2. Since both genomes contain a complete LEE (Locus of Enterocyte Effacement) island, but lack an EAF plasmid, strains RM14715 and RM14723 were classified as atypical EPEC. Furthermore, both genomes carry several putative integration sites for Stx-converting phages, implying their potential to evolve to STEC O145:H34.
Technical Abstract: Escherichia coli O145 strains RM14715 and RM14723 were isolated from wildlife feces near a leafy greens-growing region in Yuma, Arizona. Both strains carry a distinct genotype compared with the E. coli O145 strains isolated from Salinas Valley, California. Here we report complete genome sequences and annotations of RM14715 and RM14723.