Figure 3.

KEA5 and KEA6 mediate H⁺-linked K⁺ transport in bacteria. N-terminal truncations of KEA4, KEA5, and KEA6 were expressed in E. coli strains lacking K⁺ and Na⁺ transporters. A, Survival of MJF276 cells with mutated K⁺/H⁺ exchangers KefB and KefC after treatment with NEM. Shown are the colony-forming units with and without NEM treatment after appropriate serial dilutions. Data represent means and se of two biological and four technical replicates. Lettering indicates significantly different means (P < 0.05) by the one-way ANOVA test. B, EP432 cells lacking the Na⁺/H⁺ exchangers NhaA and NhaB were streaked on agar plates with LKB medium at pH 7.5 with and without supplemental NaCl and KCl as indicated. Two independent ∆KEA5 and ∆KEA6 transformants are shown. The E. coli NhaA and empty vector were used as positive and negative controls.