Influence of pH and salt condition on the membrane potential generated by <i>V</i>. <i>cholerae</i> Δ<i>pomAB</i> cells overproducing His₆-PomA together with PomB-Strep, PomB-S26A-Strep, or PomB-S26T-Strep.

<p>The fluorescence emission of the fluorophore DiOC₂ at 630 nm was determined to estimate the formation of membrane potential, ΔΨ (inside negative). Average values and standard deviations of three biological replicates, each from a different culture, are presented. <i>V</i>. <i>cholerae</i> Δ<i>nqr</i> lacks the Na⁺-translocating NADH:quinone oxidoreductase and is impaired in the formation of ΔΨ. The asterisks indicate conditions which allow only poor growth of <i>V</i>. <i>cholerae</i> Δ<i>nqr</i>, impairing determination of ΔΨ. A: LB-Na⁺; B: no salt added, with residual concentrations of 11 mM Na⁺ and 12 mM K⁺; C: LB-K⁺.