Cell-FreeEscherichia coli-Based System To Screen for Quorum-Sensing Molecules Interacting with Quorum Receptor Proteins ofStreptomyces coelicolor

Quorum sensing (QS) is mediated by small molecules and involved in diverse cellular functions, such as virulence, biofilm formation, secondary metabolism, and cell differentiation. In this study, we developed a rapid and effective screening tool based on a cell-freeEscherichia coli -based expression system to identify QS molecules ofStreptomyces . The binding of QS molecules to γ-butyrolactone receptor ScbR was monitored by changes in the expression levels of the green fluorescent protein reporter inE. coli cell extract. Using this assay system, we could successfully confirm SCB1, a γ-butyrolactone molecule inStreptomyces coelicolor , binding to its known receptor, ScbR. In addition, we have shown thatN -hexanoyl-dl -homoserine lactone, one of the QS molecules in many gram-negative bacteria, can regulate ScbR and trigger precocious antibiotic production inS. coelicolor . Our new method can be applied to other strains for which a screening tool for QS molecules has not yet been developed.