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. 1997 May;24(4):671-85. doi: 10.1046/j.1365-2958.1997.3821741.x.

Abstract

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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 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

Substances

  • Antibodies, Bacterial
  • Antigens, Bacterial
  • Bacterial Outer Membrane Proteins
  • Bacterial Proteins
  • RNA, Bacterial
  • Transcription Factors
  • bvgS protein, Bordetella pertussis
  • Niacin