SdiA, an Escherichia coli homologue of quorum-sensing regulators, controls the expression of virulence factors in enterohaemorrhagic Escherichia coli O157:H7.
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.
Kanamaru
K
K
Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-0071, Japan.
Kanamaru
K
K
Tatsuno
I
I
Tobe
T
T
Sasakawa
C
C
D001426:Bacterial Proteins / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics*; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014774:Virulence / Q000235:genetics
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C474481:EspD protein, E coli; D008565:Membrane Proteins; C097686:SdiA protein, bacteria; D015534:Trans-Activators; C490806:sdiA protein, E coli