(A) Ciprofloxacin minimum inhibitory concentration (MIC) assay against E. coli MG1655 cells in the presence or absence of Gam isoforms as indicated. Experiments were performed as described in the Materials and methods in the presence of arabinose to induce expression of the small or large isoforms of Gam. Control experiments were performed under identical conditions with the empty pBADK expression vector. (B) Disc susceptibility assays are standardised tests that quantify antibacterial susceptibility in terms of an inhibition zone diameter, and also classify bacterial strains as either resistant, or not resistant, to antibacterial agents based on expected drug efficacy in a clinical setting. The experiments were performed and interpreted in accordance with CLSI guidelines (CLSI, 2015) with a range of fluoroquinolones (CIP; ciprofloxacin, OFL; ofloxacin, NOR; norfloxacin, LEV, levoxofloxacin). Illustrative results for wild type K. pneumoniae (Ecl8) and a resistant strain (Ecl8-CIP-M2) are shown using the GamL isoform. Note that the magnification of the plates is different for the two strains as is apparent from the disc sizes. The inhibition zone diameters for all strains, with both GamL and GamS, are summarised in Table 1.