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. 1998 Jan;66(1):394-7.
doi: 10.1128/IAI.66.1.394-397.1998.

ToxR-independent expression of cholera toxin from the replicative form of CTXphi

S Lazar  1 , M K Waldor
Affiliations

ToxR-independent expression of cholera toxin from the replicative form of CTXphi

S Lazar et al. Infect Immun. 1998 Jan.

Abstract

The ctxAB operon, which encodes cholera toxin, resides in the genome of CTXphi, a filamentous bacteriophage. Within Vibrio cholerae cells, the CTXphi genome can exist either as a replicating plasmid or as a prophage integrated into the chromosome. Previous work established that ToxR is required for chromosomal ctxAB expression. We have learned that strains harboring the CTXphi replicative form produce cholera toxin under all conditions tested, independently of ToxR. During passage of CTXphi lysogens through the infant mouse intestine, transduction of CTXphi to a recipient strain can be detected, indicating that phage excision and replication occur in vivo. These results suggest that phage induction might provide a novel mechanism for the regulation of cholera toxin production.

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Figures

FIG. 1
FIG. 1
Map of the CTXφ genome. The locations of known promoters are shown with solid lines, and the postulated promoter upstream of orfU is designated with a broken line. The NotI site within the intergenic region of the phage genome where the kanamycin cassette was inserted to generate pIG is shown. The orientation of the Kmr gene is the same as that of rstR. The SphI site mutated to create pSL1 is also marked.
See this image and copyright information in PMC

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