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Escherichia coli O157:H7 Shiga toxin-encoding bacteriophages: integrations, excisions, truncations, and evolutionary implications.
J Bacteriol. 2003 Jun; 185(12):3596-605.JB

Abstract

As it descended from Escherichia coli O55:H7, Shiga toxin (Stx)-producing E. coli (STEC) O157:H7 is believed to have acquired, in sequence, a bacteriophage encoding Stx2 and another encoding Stx1. Between these events, sorbitol-fermenting E. coli O157:H(-) presumably diverged from this clade. We employed PCR and sequence analyses to investigate sites of bacteriophage integration into the chromosome, using evolutionarily informative STEC to trace the sequence of acquisition of elements encoding Stx. Contrary to expectations from the two currently sequenced strains, truncated bacteriophages occupy yehV in almost all E. coli O157:H7 strains that lack stx(1) (stx(1)-negative strains). Two truncated variants were determined to contain either GTT or TGACTGTT sequence, in lieu of 20,214 or 18,895 bp, respectively, of the bacteriophage central region. A single-nucleotide polymorphism in the latter variant suggests that recombination in that element extended beyond the inserted octamer. An stx(2) bacteriophage usually occupies wrbA in stx(1)(+)/stx(2)(+) E. coli O157:H7, but wrbA is unexpectedly unoccupied in most stx(1)-negative/stx(2)(+) E. coli O157:H7 strains, the presumed progenitors of stx(1)(+)/stx(2)(+) E. coli O157:H7. Trimethoprim-sulfamethoxazole promotes the excision of all, and ciprofloxacin and fosfomycin significantly promote the excision of a subset of complete and truncated stx bacteriophages from the E. coli O157:H7 strains tested; bile salts usually attenuate excision. These data demonstrate the unexpected diversity of the chromosomal architecture of E. coli O157:H7 (with novel truncated bacteriophages and multiple stx(2) bacteriophage insertion sites), suggest that stx(1) acquisition might be a multistep process, and compel the consideration of multiple exogenous factors, including antibiotics and bile, when chromosome stability is examined.

Authors+Show Affiliations

Children's Hospital and the University of Washington, Seattle, Washington, USA.No affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

12775697

Citation

Shaikh, Nurmohammad, and Phillip I. Tarr. "Escherichia Coli O157:H7 Shiga Toxin-encoding Bacteriophages: Integrations, Excisions, Truncations, and Evolutionary Implications." Journal of Bacteriology, vol. 185, no. 12, 2003, pp. 3596-605.
Shaikh N, Tarr PI. Escherichia coli O157:H7 Shiga toxin-encoding bacteriophages: integrations, excisions, truncations, and evolutionary implications. J Bacteriol. 2003;185(12):3596-605.
Shaikh, N., & Tarr, P. I. (2003). Escherichia coli O157:H7 Shiga toxin-encoding bacteriophages: integrations, excisions, truncations, and evolutionary implications. Journal of Bacteriology, 185(12), 3596-605.
Shaikh N, Tarr PI. Escherichia Coli O157:H7 Shiga Toxin-encoding Bacteriophages: Integrations, Excisions, Truncations, and Evolutionary Implications. J Bacteriol. 2003;185(12):3596-605. PubMed PMID: 12775697.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Escherichia coli O157:H7 Shiga toxin-encoding bacteriophages: integrations, excisions, truncations, and evolutionary implications. AU - Shaikh,Nurmohammad, AU - Tarr,Phillip I, PY - 2003/5/31/pubmed PY - 2003/7/8/medline PY - 2003/5/31/entrez SP - 3596 EP - 605 JF - Journal of bacteriology JO - J Bacteriol VL - 185 IS - 12 N2 - As it descended from Escherichia coli O55:H7, Shiga toxin (Stx)-producing E. coli (STEC) O157:H7 is believed to have acquired, in sequence, a bacteriophage encoding Stx2 and another encoding Stx1. Between these events, sorbitol-fermenting E. coli O157:H(-) presumably diverged from this clade. We employed PCR and sequence analyses to investigate sites of bacteriophage integration into the chromosome, using evolutionarily informative STEC to trace the sequence of acquisition of elements encoding Stx. Contrary to expectations from the two currently sequenced strains, truncated bacteriophages occupy yehV in almost all E. coli O157:H7 strains that lack stx(1) (stx(1)-negative strains). Two truncated variants were determined to contain either GTT or TGACTGTT sequence, in lieu of 20,214 or 18,895 bp, respectively, of the bacteriophage central region. A single-nucleotide polymorphism in the latter variant suggests that recombination in that element extended beyond the inserted octamer. An stx(2) bacteriophage usually occupies wrbA in stx(1)(+)/stx(2)(+) E. coli O157:H7, but wrbA is unexpectedly unoccupied in most stx(1)-negative/stx(2)(+) E. coli O157:H7 strains, the presumed progenitors of stx(1)(+)/stx(2)(+) E. coli O157:H7. Trimethoprim-sulfamethoxazole promotes the excision of all, and ciprofloxacin and fosfomycin significantly promote the excision of a subset of complete and truncated stx bacteriophages from the E. coli O157:H7 strains tested; bile salts usually attenuate excision. These data demonstrate the unexpected diversity of the chromosomal architecture of E. coli O157:H7 (with novel truncated bacteriophages and multiple stx(2) bacteriophage insertion sites), suggest that stx(1) acquisition might be a multistep process, and compel the consideration of multiple exogenous factors, including antibiotics and bile, when chromosome stability is examined. SN - 0021-9193 UR - https://www.unboundmedicine.com/medline/citation/12775697/Escherichia_coli_O157:H7_Shiga_toxin_encoding_bacteriophages:_integrations_excisions_truncations_and_evolutionary_implications_ L2 - http://jb.asm.org/cgi/pmidlookup?view=long&pmid=12775697 DB - PRIME DP - Unbound Medicine ER -