Affiliation:
1. Division of Geographic Medicine and Infectious Diseases, Tufts-New England Medical Center and Tufts University School of Medicine, Boston, Massachusetts 02111
Abstract
ABSTRACT
Horizontal transfer of genes encoding virulence factors has played a central role in the evolution of many pathogenic bacteria. The unexpected discovery that the genes encoding cholera toxin (
ctxAB
), the main cause of the profuse secretory diarrhea characteristic of cholera, are encoded on a novel filamentous phage named CTXΦ, has resulted in a renewed interest in the potential mechanisms of transfer of virulence genes among
Vibrio cholerae
. We describe here an alternative mechanism of cholera toxin gene transfer into nontoxigenic
V. cholerae
isolates, including strains that lack both the CTXΦ receptor, the toxin coregulated pilus (TCP), and
attRS
, the chromosomal attachment site for CTXΦ integration. A temperature-sensitive mutant of the
V. cholerae
generalized transducing bacteriophage CP-T1 (CP-T1ts) was used to transfer a genetically marked derivative of the CTX prophage into four nontoxigenic
V. cholerae
strains, including two
V. cholerae
vaccine strains. We demonstrate that CTXΦ transduced by CP-T1ts can replicate and integrate into these nontoxigenic
V. cholerae
strains with high efficiency. In fact, CP-T1ts transduces the CTX prophage preferentially when compared with other chromosomal markers. These results reveal a potential mechanism by which CTXΦ
+
V. cholerae
strains that lack the TCP receptor may have arisen. Finally, these findings indicate an additional pathway for reversion of live-attenuated
V. cholerae
vaccine strains.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
46 articles.
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