SdiA, an Escherichia coli homologue of quorum-sensing regulators, controls the expression of virulence factors in enterohaemorrhagic Escherichia coli O157:H7

Mol Microbiol. 2000 Nov;38(4):805-16. doi: 10.1046/j.1365-2958.2000.02171.x.


The quorum-sensing system in bacteria is a well-known regulatory system that controls gene expression in a cell density-dependent manner. A transcriptional regulator (LuxR homologue), signal synthase (LuxI homologue) and autoinducer (acyl homoserine lactone) are indispensable for this system in most Gram-negative bacteria. In this study, we found that SdiA, an Escherichia coli LuxR homologue, is a negative regulator of the expression of virulence factors EspD and intimin in enterohaemorrhagic E. coli (EHEC) O157:H7. The expression of EspD and intimin was inhibited at the RNA level upon SdiA overexpression. SdiA has a DNA-binding motif in its C-terminal part and can bind to the promoter regions of the esp and eae genes in vitro. Extracellular factors, which accumulate in culture supernatants of O157:H7 at the stationary phase of growth and inhibit EspD and intimin synthesis, bind to the N-terminal part of SdiA in vivo and in vitro. O157:H7 overproducing the N-terminal part of SdiA exhibited hypertranscription of EspD and intimin, suggesting that the overproduced N-terminal part had inhibited the activity of intact SdiA through titration of the extracellular factors. These results indicate that a quorum-sensing system including the SdiA protein controls colonization by O157:H7.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Escherichia coli / genetics*
  • Escherichia coli / metabolism
  • Escherichia coli / pathogenicity*
  • Escherichia coli Infections / microbiology*
  • Escherichia coli Proteins*
  • Gene Expression Regulation, Bacterial*
  • Genes, Bacterial
  • Membrane Proteins / biosynthesis
  • Membrane Proteins / genetics*
  • Trans-Activators / genetics*
  • Trans-Activators / metabolism
  • Virulence / genetics


  • Bacterial Proteins
  • Escherichia coli Proteins
  • EspD protein, E coli
  • Membrane Proteins
  • SdiA protein, bacteria
  • Trans-Activators
  • sdiA protein, E coli