(a to e) Schematic overview and results of the transposon library screen to identify genes involved in NaCl-induced colistin resistance. Representative growth analyses of mutants identified in the transposon screen. Bacteria were challenged with 2 mg/liter colistin in Mueller-Hinton broth (MHB) with or without 154 mM NaCl, and growth was measured after 20 to 24 h. Mutants are grouped according to the annotations of the disrupted genes, which can be found in Table 2. Data represent the averages of results of three biological replicates, and error bars indicate the SDs from the means. Statistical significance was determined by one-way analysis of variance (ANOVA), and only mutants whose growth differed significantly from that of the wild type are shown. (f) Schematic overview of the A1S_0430 genomic locus in the transposon mutant 5A7 and the targeted deletion mutant, the ΔlpsB strain.