Dataset Information

Variability in the Occupancy of Escherichia coli O157 Integration Sites by Shiga Toxin-Encoding Prophages.

ABSTRACT: Escherichia coli O157:H7 strains often produce Shiga toxins encoded by genes on lambdoid bacteriophages that insert into multiple loci as prophages. O157 strains were classified into distinct clades that vary in virulence. Herein, we used PCR assays to examine Shiga toxin (Stx) prophage occupancy in yehV, argW, wrbA, and sbcB among 346 O157 strains representing nine clades. Overall, yehV was occupied in most strains (n = 334, 96.5%), followed by wrbA (n = 213, 61.6%), argW (n = 103, 29.8%), and sbcB (n = 93, 26.9%). Twelve occupancy profiles were identified that varied in frequency and differed across clades. Strains belonging to clade 8 were more likely to have occupied sbcB and argW sites compared to other clades (p < 0.0001), while clade 2 strains were more likely to have occupied wrbA sites (p < 0.0001). Clade 8 strains also had more than the expected number of occupied sites based on the presence of stx variants (p < 0.0001). Deletion of a 20 kb non-Stx prophage occupying yehV in a clade 8 strain resulted in an ~18-fold decrease in stx2 expression. These data highlight the complexity of Stx prophage integration and demonstrate that clade 8 strains, which were previously linked to hemolytic uremic syndrome, have unique Stx prophage occupancy profiles that can impact stx2 expression.

SUBMITTER: Henderson ST

PROVIDER: S-EPMC8309913 | biostudies-literature | 2021 Jun

REPOSITORIES: biostudies-literature

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Variability in the Occupancy of Escherichia coli O157 Integration Sites by Shiga Toxin-Encoding Prophages.

Henderson Scott T ST Singh Pallavi P Knupp David D Lacher David W DW Abu-Ali Galeb S GS Rudrik James T JT Manning Shannon D SD

Toxins 20210622 7

Escherichia coli O157:H7 strains often produce Shiga toxins encoded by genes on lambdoid bacteriophages that insert into multiple loci as prophages. O157 strains were classified into distinct clades that vary in virulence. Herein, we used PCR assays to examine Shiga toxin (Stx) prophage occupancy in yehV, argW, wrbA, and sbcB among 346 O157 strains representing nine clades. Overall, yehV was occupied in most strains (n = 334, 96.5%), followed by wrbA< ...[more]

PMID: 34206386

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Project description:Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a foodborne pathogen producing Shiga toxins (Stx1 and Stx2), which can cause hemorrhagic diarrhea and life-threatening infections. O157:H7 strain EDL933 carries prophages CP-933V and BP-933W, which encode Shiga toxin genes (stx1 and stx2, respectively). The aim of this work was to investigate the mechanisms of adaptive resistance of EHEC strain EDL933 to a typically lethal dose of gamma irradiation (1.5 kGy). Adaptive selection through six passages of exposure to 1.5 kGy resulted in the loss of CP-933V and BP-933W prophages from the genome and mutations within three genes: wrbA, rpoA, and Wt_02639 (molY). Three selected EHEC clones that became irradiation adapted to the 1.5-kGy dose (C1, C2, and C3) demonstrated increased resistance to oxidative stress, sensitivity to acid pH, and decreased cytotoxicity to Vero cells. To confirm that loss of prophages plays a role in increased radioresistance, clones C1 and C2 were exposed to bacteriophage-containing lysates. Although phage BP-933W could lysogenize C1, C2, and E. coli K-12 strain MG1655, it was not found to have integrated into the bacterial chromosome in C1-Φ and C2-Φ lysogens. Interestingly, for the E. coli K-12 lysogen (K-12-Φ), BP-933W DNA had integrated at the wrbA gene (K-12-Φ). Both C1-Φ and C2-Φ lysogens regained sensitivity to oxidative stress, were more effectively killed by a 1.5-kGy gamma irradiation dose, and had regained cytotoxicity and acid resistance phenotypes. Further, the K-12-Φ lysogen became cytotoxic, more sensitive to gamma irradiation and oxidative stress, and slightly more acid resistant. IMPORTANCE Gamma irradiation of food products can provide an effective means of eliminating bacterial pathogens such as enterohemorrhagic Escherichia coli (EHEC) O157:H7, a significant foodborne pathogen that can cause severe disease due to the production of Stx. To decipher the mechanisms of adaptive resistance of the O157:H7 strain EDL933, we evolved clones of this bacterium resistant to a lethal dose of gamma irradiation by repeatedly exposing bacterial cells to irradiation following a growth restoration over six successive passages. Our findings provide evidence that adaptive selection involved modifications in the bacterial genome, including deletion of the CP-933V and BP-933W prophages. These mutations in EHEC O157:H7 resulted in loss of stx1 and stx2, loss of cytotoxicity to epithelial cells, and decreased resistance to acidity, critical virulence determinants of EHEC, concomitant with increased resistance to lethal irradiation and oxidative stress. These findings demonstrate that the potential adaptation of EHEC to high doses of radiation would involve elimination of the Stx-encoding phages and likely lead to a substantial attenuation of virulence.

Dataset Information

Variability in the Occupancy of Escherichia coli O157 Integration Sites by Shiga Toxin-Encoding Prophages.

Publications

Variability in the Occupancy of <i>Escherichia coli</i> O157 Integration Sites by Shiga Toxin-Encoding Prophages.

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