(A) Antibacterial activity of l-EP and cisplatin against E. coli K12 and CFT073. Relative OD600 refers to the OD600 value of the treated sample divided by that of the untreated control (mean ± standard deviation, n = 6 for K12 experiments, n = 7 for CFT073 and l-EP, n = 4 for CFT073 and cisplatin). Statistical differences compared to untreated controls were calculated using two-tailed student t test assuming unequal variances; ****P < 0.0001, ***P < 0.001, **P < 0.01; (B) Representative phase-contrast micrographs of E. coli K12 and CFT073 treated with l-EP. Scale bar: 10 µm. All assays were performed in modified M9 medium (11 h, 30 °C with shaking).