Figure 5.

Aminoglycosides do not induce the expression of aminoglycoside resistance cassettes. (A) Violin plots showing the induction ratios of all cassettes in the presence of four inducing aminoglycosides, and the non-inducing neomycin. Color code of the dots as in Figure 4. Median and quartiles are represented by dashed lines. Linear regression analysis did not find significant differences (P > 0.3) in fluorescence readings in the absence versus the presence of Ags. A linear mixed model revealed statistically significant differences for gentamicin and amikacin, but they were mild, and in opposite direction (see text and Supplementary Figure S4). This suggests that aminoglycosides do not induce the expression of AgR cassettes. Each data point represents the mean of at least three measurements. (B) Induction ratio measured through Western blot of the 10 cassettes with highest and lowest IRs in kanamycin measured by flow cytometry (orange and violet boxes in panel A). GFP abundance was normalized to DnaK. Cytometry and Western blot results do not correlate (inset: linear regression R²= 0.02), suggesting that the distribution of IRs in cytometry does not reflect a biologically relevant induction (i.e. these values are not the consequence of a specific interaction between the antibiotic and the 5′ UTRs of this subset of genes). See also Supplementary Figures S2–S4.