Control of the Salmonella ugd gene by three two-component regulatory systems

Mol Microbiol. 2003 Jan;47(2):335-44. doi: 10.1046/j.1365-2958.2003.03318.x.


The Salmonella ugd gene is required for the incorporation of 4-aminoarabinose in the lipopolysaccharide and resistance to the antibiotic polymyxin B. Transcription of the ugd gene is induced by Fe3+ via the PmrA-PmrB two-component system and by low Mg2+ in a process that requires the PhoP-PhoQ two-component system, the PhoP-activated PmrD protein and the PmrA-PmrB system. Here, we establish that mutation of the tolB gene promotes ugd transcription independently of both the PhoP-PhoQ and PmrA-PmrB systems. This activation is mediated by the RcsC-YojN-RcsB phosphorelay and the RcsA protein, suggesting a role for ugd in capsule synthesis. Binding sites for the RcsB, PmrA and PhoP proteins were identified in the ugd promoter. Although the PmrA-PmrB and RcsC-YojN-RcsB systems promoted ugd transcription independently of the PhoP-PhoQ system under different environmental conditions, ugd expression inside macrophages was strictly dependent on PhoP-PhoQ, suggesting that low Mg2+ is a cue for the intracellular environment.

Publication types

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

MeSH terms

  • Animals
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Base Sequence
  • Enhancer Elements, Genetic
  • Gene Expression Regulation, Bacterial*
  • Macrophages / microbiology
  • Mice
  • Molecular Sequence Data
  • Mutation
  • Phosphorylation
  • Promoter Regions, Genetic
  • Salmonella / enzymology*
  • Salmonella / genetics
  • Salmonella / growth & development
  • Signal Transduction*
  • Transcription, Genetic
  • Uridine Diphosphate Glucose Dehydrogenase / chemistry
  • Uridine Diphosphate Glucose Dehydrogenase / genetics*
  • Uridine Diphosphate Glucose Dehydrogenase / metabolism*


  • Bacterial Proteins
  • Uridine Diphosphate Glucose Dehydrogenase