Synergy Screening Identifies a Compound That Selectively Enhances the Antibacterial Activity of Nitric Oxide

Abstract

Antibiotic resistance poses a serious threat to global health. To reinforce the antiinfective arsenal, many novel therapeutic strategies to fight bacterial infections are being explored. Among them, anti-virulence therapies, which target pathways important for virulence, have attracted much attention. Nitric oxide (NO) defense systems have been identified as critical for the pathogenesis of various bacteria, making them an appealing therapeutic target. In this study, we performed chemical screens to identify inhibitors of NO detoxification in Escherichia coli. We found that 2-mercaptobenzothiazole (2-MBT) can potently inhibit cellular detoxification of NO, achieving a level of inhibition that resembled the effect of genetically removing Hmp, the dominant detoxification enzyme under oxygenated conditions. Further analysis revealed that in the presence of NO, 2-MBT impaired the catalysis of Hmp and synthesis of Hmp and other proteins, whereas in its absence there were minimal perturbations to growth and protein synthesis. In addition, by studying the structure-activity relationship of 2-MBT, we found that both sulfur atoms in 2-MBT were vital for its inhibition of NO detoxification. Interestingly, when 2-mercaptothiazole (2-MT), which lacked the benzene ring, was used, differing biological activities were observed, although they too were NO dependent. Specifically, 2-MT could still prohibit NO detoxification, though it did not interfere with Hmp catalysis; rather, it was a stronger inhibitor of protein synthesis and it reduced the transcript levels of hmp, which was not observed with 2-MBT. Overall, these results provide a strong foundation for further exploration of 2-MBT and 2-MT for therapeutic applications.

Pseudomonas aeruginosa prioritizes detoxification of hydrogen peroxide over nitric oxide

“…Looking forward, understanding the mechanistic bases of prioritized detoxification could lead to strategies to treat bacteria that use NO and H 2 O 2 detoxification systems to enhance their virulence [ 9 ]. Such an anti-infective approach is currently being explored [ 35 ], along with other alternative treatments [ 36 – 40 ], with the ultimate goal of complementing currently available antibiotics.…”

Discovery, Characterization, and Bioactivity of the Achromonodins: Lasso Peptides Encoded by Achromobacter

“…The outer membrane of Gram-negative bacteria is a major barrier for entry of many antibiotics otherwise active against Gram-positive bacteria. − While we observed no activity of achromonodin-1 against wild-type E. coli MG1655, we observed single-digit micromolar (MIC of 2.5 μM) activity against the E. coli imp4213 strain (Figure S14), a mutant strain with increased permeability of the outer membrane. − Other RNAP-inhibiting lasso peptides cross the inner membrane via the proton gradient powered SbmA in E. coli , or the ABC transporter YddA in Burkholderia …”

Antimicrobial Lasso Peptide Cloacaenodin Utilizes a Unique TonB-Dependent Transporter to Access Susceptible Bacteria

“…As a result of this genetic defect, the outer leaflet of the OM of this strain is irregularly enriched in phospholipids, which in turn leads to enhanced permeability of compounds normally excluded. Previous studies have employed the use of this strain for toxicity screens of compounds so that the OM barrier plays a minimal role in the screen. − We found that cloacaenodin, when applied extracellularly in a spot-on-lawn assay, had no activity against E. coli MC4100 (Figure A), but it had potent, low micromolar activity (MIC ≤ 1.9 μM) against E. coli imp4213 (Figure B).…”