FIG 1.

Identification of FRD as a gene responsible for persistence. (A) Plasmids screened by means of the procedure shown in Fig. S1 in the supplemental material and which conferred tolerance against Amp. (B) The P3 plasmid increased the persister frequency in the presence of Nor. (C) Fumarate and FRD elevated the persister frequency synergistically. (D) Preexposure of cells to fumarate increased the frequency of persisters in the presence of all three major classes of antibiotics (Amp, Kan, and Nor). (E) Deletion of dctA (dicarboxylate and fumarate transporter) strongly attenuated the effect of fumarate preexposure on the persister frequency in the presence of Nor. WT, wild type. *, P < 0.05; **, P < 0.01. Experiments were performed in triplicate.