Chemical Probes that Target a Dissociative LuxR-Type Quorum Sensing Receptor in Gram-Negative Bacteria

Area of Science:

• Microbiology and Molecular Biology
• Chemical Biology
• Bacterial Pathogenesis

Background:

• Quorum sensing (QS) enables bacteria to coordinate behaviors based on cell density.
• LuxR-type receptors, common in Gram-negative bacteria, regulate gene expression in response to N-acyl l-homoserine lactone (AHL) signals.
• Dissociative LuxR-type receptors bind DNA without a ligand and detach upon ligand binding, unlike associative receptors.

Purpose of the Study:

• To discover synthetic modulators of EsaR, a dissociative LuxR-type receptor in *Pantoea stewartii*.
• To investigate chemical features influencing EsaR activity and understand dissociative vs. associative LuxR mechanisms.
• To explore new chemical tools for studying bacterial QS.

Main Methods:

• Design and synthesis of AHL-scaffold-based compounds.
• Evaluation of compound activity using cell-based EsaR reporters.
• Phenotypic assays to assess the impact of compounds on bacterial behavior.

Main Results:

• Identified synthetic compounds exhibiting agonistic activity on the EsaR receptor.
• Determined specific compound features associated with EsaR activation.
• No antagonistic compounds targeting EsaR were discovered, contrasting with studies of other LuxR-type receptors.

Conclusions:

• The study provides novel chemical tools to probe the mechanisms of ligand response in dissociative LuxR-type receptors like EsaR.
• Findings highlight key structural differences between associative and dissociative LuxR receptor ligand interactions.
• Developing competitive antagonists for dissociative LuxR receptors may require alternative chemical strategies.