Role of the LuxR solo, SdiA, in eavesdropping on foreign bacteria

Bacteria can cooperate by coordinating their gene expression through the production, release, and detection of small molecules, a phenomenon known as quorum sensing (QS). One type of QS commonly found in Gram-negative bacteria utilizes a LuxI-type enzyme to produce a signaling molecule of the N-acyl-homoserine lactone (AHL) family, and a transcription factor of the LuxR family to detect and respond to the AHL. In a subset of Enterobacteriaceae, including Escherichia coli and Salmonella, no LuxI family member is present and no AHLs are synthesized. However, they encode a LuxR family member, SdiA, that is used to detect the QS molecules of other bacterial species, a behavior known as eavesdropping. Despite significant research on the topic, the overall role of SdiA-mediated eavesdropping in these bacteria remains unclear. In this review, we discuss the phenotypes and regulons of SdiA in the Enterobacteriaceae.