Fig. 1: NQNO has selective antibiotic activity against N. gonorrhoeae.

a, Structure of the synthesized 2-alkyl-4-quinolones and corresponding N-oxides of P. aeruginosa. b, Growth curves of N. gonorrhoeae MS11 and N. cinerea incubated with 5, 10, 25 or 50 µM of NQ, trans-Δ¹-NQ, NQNO or trans-Δ¹-NQNO; control cultures were grown with 1% solvent (DMSO). Growth was monitored using OD₅₅₀ readings every 30 min. Data are representative of 3 independent experiments. c, Effect of NQ, trans-Δ¹-NQ, NQNO or trans-Δ¹-NQNO on the growth of different gonococcal strains and Neisseria species. Growth was measured as in b and quantified using area under the growth curve. The colour gradient indicates growth compared to control (1% DMSO), from no growth (90–100% inhibition of growth, white) to full growth (0–10% inhibition of growth, dark green). d, Growth of N. gonorrhoeae WHO reference strains in the presence of 5, 10, 25 or 50 µM of NQNO. Control cultures were grown with 1% DMSO. Growth was monitored as in b.