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J. Bacteriol., 05 1995, 2727-2736, Vol 177, No. 10
TJ Merkel and S Stibitz
In Bordetella pertussis, the coordinate regulation of virulence factor
expression is controlled by the products of the bvgAS locus. In the
presence of modulating signals such as MgSO4, nicotinic acid, or reduced
temperature, the expression of bvg-activated genes is reduced while the
expression of bvg-repressed genes is induced. One model for the regulation
of bvg-repressed genes predicts the existence of a repressor protein
encoded by a bvg-activated gene. Once activated, the product of this
bvg-activated gene would bind to and repress transcription from the
bvg-repressed genes. We isolated five genetically independent transposon
insertion mutants of B. pertussis that have a phenotype consistent with the
knockout of a putative bvg- regulated repressor. These mutants
constitutively expressed a vrg6-phoA transcriptional fusion but
demonstrated normal bvgAS function. Genomic mapping and DNA sequence
analysis of the sites of transposon insertion demonstrated that these
mutants define a locus downstream of bvgAS. Introduction of an in-frame,
12-bp insertion within this locus also conferred the mutant phenotype,
confirming that the phenotype seen in the transposon mutants is the result
of disruption of a distinct gene, which we have designated bvgR, and is not
a consequence of polar effects on bvgAS.
Copyright © 1995, American Society for Microbiology
Identification of a locus required for the regulation of bvg-repressed genes in Bordetella pertussis
National Institute of Dental Research, NIH, Bethesda, MD 20892, USA.
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