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Cotter, PA and Miller, JF (1997) A mutation in the Bordetella bronchiseptica bvgS gene results in reduced virulence and increased resistance to starvation, and identifies a new class of Bvg-regulated antigens. Mol. Microbiol. 24:671-85
The Bordetella BvgAS signal-transduction system has traditionally been viewed as mediating a transition between two distinct phenotypic phases: the Bvg+ phase, characterized by the expression of adhesins and toxins, and the Bvg-phase, characterized by motility in Bordetella bronchiseptica and by the expression of vrg loci in Bordetella pertussis. In B. bronchiseptica, the Bvg+ phase is necessary and sufficient for respiratory tract colonization whereas the Bvg phase is required for growth under nutrient-limiting conditions. This report describes the characterization of a mutant that is locked in a Bvg-intermediate (Bvg[i]) phase. The mutation conferring this phenotype, designated bvgS-I1, results in a threonine-to-methionine substitution near the primary site of phosphorylation in BvgS. Compared to its Bvg+-phase-locked parent, the Bvg(i) mutant displays increased resistance to nutrient limitation and reduced virulence. Molecular analyses indicate that the mutant has lost the ability to express a subset of Bvg+-phase factors and has gained the ability to express factors unique to the Bvg(i) phase. Although identified by mutation, this work indicates that the Bvg(i) phase is expressed by wild-type B. bronchiseptica in response to certain (semi-modulating) environmental conditions. The identification of Bvg(i)-specific antigens suggests the existence of a new class of Bvg-regulated genes. We hypothesize that BvgAS is capable of mediating the expression of a spectrum of phenotypic phases in response to the various environments encountered as Bordetella travels within and between mammalian hosts.
Amino Acid Sequence; Animals; Antibodies, Bacterial/immunology; Antigens, Bacterial/genetics; Bacterial Outer Membrane Proteins/genetics; Bacterial Proteins/genetics; Bordetella bronchiseptica/genetics; Bordetella bronchiseptica/metabolism; Bordetella bronchiseptica/pathogenicity; Female; Gene Expression Regulation, Bacterial; Genes, Bacterial; Molecular Sequence Data; Mutation; Niacin/metabolism; RNA, Bacterial/genetics; Rats; Rats, Wistar; Signal Transduction; Transcription Factors/genetics; Transcription, Genetic
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Table 1. shows several BvgS mutants with reduced virulence (Bvg- or Bvgi).
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