Combination of gallium(iii) with acetate for combating antibiotic resistant Pseudomonas aeruginosa

Gallium(iii) has been widely used as a diagnostic and therapeutic agent in clinics for the treatment of various diseases, in particular, Ga-based drugs have been exploited as antimicrobials to combat the crisis of antimicrobial resistance. The therapeutic properties of Ga(iii) are believed to be attributable to its chemical similarity to Fe(iii). However, the molecular mechanisms of action of gallium remain unclear. Herein, by integrating metalloproteomics with metabolomics and transcriptomics, we for the first time identified RpoB and RpoC, two subunits of RNA polymerase, as Ga-binding proteins in Pseudomonas aeruginosa. We show that Ga(iii) targets the essential transcription enzyme RNA polymerase to suppress RNA synthesis, resulting in reduced metabolic rates and energy utilization. Significantly, we show that exogenous supplementation of acetate could enhance the antimicrobial activity of Ga(iii), evidenced by the inhibited growth of persister cells and attenuated bacterial virulence. The effectiveness of co-therapy of Ga(iii) and acetate was further validated in mammalian cell and murine skin infection models, which is attributable to enhanced uptake of Ga(iii), and reduced TCA cycle flow and bacterial respiration. Our study provides novel insights into the mechanistic understanding of the antimicrobial activity of Ga(iii) and offers a safe and practical strategy of using metabolites to enhance the efficacy of Ga(iii)-based antimicrobials to fight drug resistance.