Transcriptomic Impact of Phage Carriage in Two Isogenic O157:H7 Enterohemorrhagic Escherichia Coli




Martinez, Ricardo Armando

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Enterohemorrhagic Escherichia coli (EHEC) of the O157:H7 serotype have been responsible for outbreaks of human disease since their discovery in 1982. The chief virulence trait found in many O157 EHEC is the carriage of one or more Shiga-toxin (Stx) encoding prophages. In non-EHEC backgrounds, Stx-phage carriage has been implicated in the regulation of virulence and metabolic loci. In this study, we examine the impact of phage carriage in a native O157:H7 background using two strains whose core genomes are identical at the SNP level with the key distinction that one lacks two Stx-encoding phages and one other phage region. Using an RNAseq approach, we examine mRNA transcripts and smRNA expression profiles with read data obtained from TT12A (stx+) and TT12B (stx-) under spontaneous and phage-inducing conditions. Total RNA was extracted using the Ambion Purellink kit, and mRNA was subsequently enriched with the MICROBExpress kit, both used according to manufacturer instructions. For smRNA analysis, paired-end libraries were prepared using the TriLink Cleantag small RNA kit. RNA was sequenced using the Illumina NextSeq 500 platform, and analysis of RNAseq reads was performed using tools such as Geneious, Galaxy, and Degust. Analysis revealed differential expression of virulence factors as well as loci associated with anaerobic metabolism, such as those of the tor operon. Taken together, the findings in this study demonstrate that phage carriage may possess global regulatory roles in an O157:H7 background.


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EHEC, Enterohemorrhagic Escherichia coli, O157, Shiga toxin Phage



Integrative Biology