Researchers are exploring whether these ubiquitous fluorinated molecules might worsen infections or hamper vaccine effectiveness.
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Edited by John J. Mekalanos, Harvard Medical School, Boston, MA, and approved June 15, 1999 (received for review April 2, 1999)
Abstract
Salmonella typhimurium employs the specialized type III secretion system encoded in pathogenicity island 1 (SPI1) to translocate effector proteins into host cells and to modulate host cell signal transduction. The SPI1 type III system and the effector proteins are conserved among all salmonellae and are thought to be acquired by horizontal gene transfer. The genetic mechanisms mediating this horizontal transfer are unknown. Here, we describe that SopE, a SPI1-dependent translocated effector protein, is present in relatively few S. typhimurium isolates. We have isolated a temperate phage that encodes SopE. Phage morphology and DNA hybridization, as well as partial sequence information, suggest that this phage (SopEΦ) is a new member of the P2 family of bacteriophages. By lysogenic conversion this phage can horizontally transfer genes between different S. typhimurium strains. Strikingly, most of the isolates harboring SopEΦ belong to the small group of epidemic strains of S. typhimurium that have been responsible for a large percentage of human and animal salmonellosis and have persisted for a long period of time. Our data suggest that horizontal transfer of type III dependent effector proteins by lysogenic infection with bacteriophages (lysogenic conversion) may provide an efficient mechanism for fine-tuning the interaction of Salmonella spp. with their hosts.
Footnotes
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↵§ To whom reprint requests should be addressed. E-mail: hardt{at}m3401.mpk.med.uni-muenchen.de.
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This paper was submitted directly (Track II) to the Proceedings Office.
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Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. AF153829).
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A Commentary on this article begins on page 9452.
ABBREVIATIONS
- PFGE,
- pulsed-field gel electrophoresis;
- pfu,
- plaque-forming unit;
- SARA,
- Salmonella reference collection A
- Received April 2, 1999.
- Copyright © 1999, The National Academy of Sciences
Isolation of a temperate bacteriophage encoding the type III effector protein SopE from an epidemic Salmonella typhimurium strain
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