Fig. 4.

Effect of potassium concentration in tolerance to formic acid of yeast cells with different capacities of K⁺ uptake. Comparison of the susceptibility of wild-type (wt) BY4741, trk1Δ and trk2Δ deletion mutants to different concentrations of formic acid (0, 10, 20, 30, 40 and 50 mM) in ammonium phosphate medium supplemented with increasing concentrations of KCl (0.5, 2 and 20 mM). Serial dilutions (1:0, 1:3 and 1:15) of a water-diluted cellular suspension with an OD₆₀₀ of 0.05 were spotted onto agar plates and incubated during 5 days at 30 °C