Role for a Phage Promoter in Shiga Toxin 2 Expression from a Pathogenic Escherichia coli Strain

Author:

Wagner Patrick L.1,Neely Melody N.2,Zhang Xiaoping1,Acheson David W. K.1,Waldor Matthew K.31,Friedman David I.2

Affiliation:

1. Division of Geographic Medicine and Infectious Diseases, Tufts University School of Medicine, Boston, Massachusetts 021111;

2. Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan 481092

3. Howard Hughes Medical Institute3 and

Abstract

ABSTRACT Shiga toxins (Stxs), encoded by the stxA and stxB genes, are important contributors to the virulence of Escherichia coli O157:H7 and other Stx-producing E. coli (STEC) strains. The stxA and stxB genes in STEC strains are located on the genomes of resident prophages of the λ family immediately downstream of the phage late promoters ( p R′ ). The phage-encoded Q proteins modify RNA polymerase initiating transcription at the cognate p R′ promoter which creates transcription complexes that transcend a transcription terminator immediately downstream of p R′ as well as terminator kilobases distal to p R′ . To test if this Q-directed processive transcription plays a role in stx 2 AB expression, we constructed a mutant prophage in an O157:H7 clinical isolate from which p R′ and part of Q were deleted but which has an intact p Stx, the previously described stx 2 AB -associated promoter. We report that production of significant levels of Stx2 in this O157:H7 isolate depends on the p R′ promoter. Since transcription initiating at p R′ ultimately requires activation of the phage lytic cascade, expression of stx 2 AB in STEC depends primarily on prophage induction. By showing this central role for the prophage in stx 2 AB expression, our findings contradict the prevailing assumption that phages serve merely as agents for virulence gene transfer.

Publisher

American Society for Microbiology

Subject

Molecular Biology,Microbiology

Reference41 articles.

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3. Ausubel F. M. Brent R. Kingston R. E. Moore D. D. Seidman J. G. Smith J. A. Struhl K. Current protocols in molecular biology. 1999 John Wiley & Sons Inc. New York N.Y

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5. A bacterial virulence determinant encoded by lysogenic coliphage lambda;Barondess J. J.;Nature,1990

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