Two novel regulatory genes, fliT and fliZ, in the flagellar regulon of Salmonella

Genes Genet Syst. 1999 Dec;74(6):287-92. doi: 10.1266/ggs.74.287.


The flagellar operons of Salmonella are divided into three classes with respect to their transcriptional hierarchy. Expression of the class 2 operons requires the class 1 gene products, FlhD and FlhC, and is increased by mutation in the flgM gene, which encodes a class 3-specific anti-sigma factor. Here we report the identification of two novel regulatory genes for class 2 transcription. Presence of the fliZ and fliT genes on multicopy plasmids enhanced and inhibited, respectively, transcription from a chromosomal class 2 promoter. Disruption of the fliZ and fliT genes on the chromosome decreased and increased, respectively, class 2 expression. These results suggest that the fliZ and fliT genes may encode positive and negative regulatory factors, respectively, for class 2 expression. Enhancement of class 2 expression by the flgM mutation was cancelled by the coexisting fliZ mutation, indicating that FliZ is essential for this enhancement.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Escherichia coli Proteins
  • Flagella / genetics*
  • Gene Expression Regulation, Bacterial
  • Genes, Regulator
  • Membrane Proteins*
  • Molecular Chaperones*
  • Mutation
  • Operon
  • Salmonella / genetics*
  • Sigma Factor / genetics
  • Sigma Factor / metabolism
  • Trans-Activators / genetics
  • Trans-Activators / metabolism


  • Bacterial Proteins
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • FliA protein, Bacteria
  • Membrane Proteins
  • Molecular Chaperones
  • Sigma Factor
  • Trans-Activators
  • flhD protein, E coli
  • FlgM protein, Bacteria
  • fliZ protein, Bacillus subtilis
  • fliT protein, Bacteria