Submitted to: Foodborne Pathogens and Disease
Publication Type: Review Article
Publication Acceptance Date: 9/30/2010
Publication Date: 2/1/2011
Citation: Smith, J.L., Fratamico, P.M., Yan, X. 2011. Eavesdropping by bacteria: the role of SdiA in Escherichia coli and Salmonella enterica serovar Typhimurium quorum sensing. Foodborne Pathogens and Disease. 8:169-178.
Technical Abstract: Many gram-negative bacteria utilize N-acyl-L-homoserine lactones (AHLs) to sense and respond to their own population densities and to regulate gene transcription. The AHLs, produced by AHL synthases, bind to receptors belonging to the LuxR family of transcriptional regulators leading to activation or repression of target genes. Escherichia coli and Salmonella enterica contain a LuxR-homolog, SdiA, but do not synthesize AHLs since they lack AHL synthase enzymes. However, SdiA can bind AHLs produced by other bacterial species allowing E. coli and S. enterica to regulate gene transcription. Many of the studies on the effect of SdiA have been done utilizing the sdiA gene expressed from a multicopy plasmid rather than depending on expression of the chromosomal gene. Overexpression of the gene does not necessarily reflect the true physiological status of the activity of the sdiA gene. The S. Typhimurium chromosomal sdiA gene is involved in the action of the rck gene, which mediates the adhesion and invasion of epithelial cells and is involved in the resistance of the organism to complement. The E. coli chromosomal sdiA gene upregulates the gadA gene, a key component in resistance of the organism to acidic conditions and plays a role in virulence of E. coli O157:H7 by regulating the expression of certain genes in the LEE locus. In addition, the chromosomal sdiA gene has a role in the transport and processing of the AI-2 molecule. The SdiA-AHL complex inhibits motility and biofilm formation in E. coli. It is probable that the sdiA gene plays other important roles in S. enterica and E. coli and more research is needed.