The usnic acid derivative peziculone targets cell walls of Gram-positive bacteria revealed by high-throughput CRISPRi-seq analysis

Usnic acid, a representative dibenzofuran metabolite, is known to have antimicrobial properties. However, despite considerable interest as an antimicrobial agent, the mechanism by which usnic acid and its derivatives exert their action is not fully characterized. Herein, we describe the synthesis of peziculone a 5:1 equilibrium mixture of two inseparable usnic acid derivatives, peziculone A (1) and peziculone B (2). We demonstrate the antibacterial activity of peziculone against several Gram-positive bacterial pathogens is significantly better than usnic acid. Using CRISPRi-seq analysis together with membrane fluorescent staining approach, we demonstrate that peziculone destabilizes the cell wall of Gram-positive bacteria. Additionally, we show that peziculone treatment at 2.5 and 3.5 μg/ml impairs cell surface appendages and biofilm formation by S. aureus. Taken together, our data demonstrate that a derivative compound of usnic acid peziculone has significant antimicrobial activity against Gram-positive bacteria by targeting the cell wall, which provides a platform for developing novel anti-bacterial drugs.