Figure 5.

Persister Formation Frequency Positively Correlates with Efflux Gene Expression Level and Negatively Correlates with Intracellular Antibiotic Accumulation. Antibiotics Lethal Effects Were Enhanced by Addition of Efflux Inhibitors

(A) Relative tolC expression level of the four strains measured by qPCR. WT (wild-type strain BW25113), OVER (tolC overexpression strain, by pBAD::tolC in BW25113, induced by 10^-5% arabinose), ΔtolC (tolC knockout strain, Key::JW5503), and RESC (tolC rescued strain, by pBAD::tolC in ΔtolC strain, induced by 10^-6% arabinose).

(B) Relative antibiotic accumulation in the four strains determined by fluorescence microscopy.

(C) Persister formation frequency of the four strains determined by antibiotic susceptibility measurement. The correlation coefficiency between intracellular antibiotic accumulation level and tolC expression level is −0.776; between intracellular antibiotic accumulation level and probability of persistence is −0.989; between tolC expression level and probability of persistence is 0.848.

(D–G) (D) Persister formation frequency of the four strains under antibiotic treatment of different concentrations. Antibiotics lethal effects were enhanced by efflux inhibitors; carbenicillin (E), cloxacillin (F), and nalidixic acid (G). Abbreviations: Car, carbenicillin. NA, nalidixic acid. Clo, cloxacillin. PAβN, Phenylalanine arginyl β-naphthylamide. NMP, 1-(1-Naphthylmethyl) piperazine. The bars indicate mean of at least three independent experiments; error bar indicates SD (^∗p value < 0.1; ^∗∗p value < 0.01; ^∗∗∗p value < 0.001; ^∗∗∗∗p value < 0.0001).

See also Figure S4.