Fig. 2.

The expression of HAA1 and of Haa1-regulated genes is required for S. cerevisiae adaptation and tolerance to formic acid. a Cells of the parental strain (squares) and deletion mutant haa1Δ (diamons) were grown in liquid MMB medium (pH 4.0) supplemented (closed symbols), or not (open symbols), with 30 mM of formic acid (upper panel) and growth was followed based on culture optical density at 600 nm (OD₆₀₀). Cell viability (CFU ml⁻¹) was also determined during cultivation (lower panel). b Growth curves of the parental BY4741 strain and of strains with the Haa1-target genes deleted were incubated in liquid MMB medium (pH 4.0) supplemented with 30 mM of formic acid. The growth curves indicated in panels (a) and (b) are representative of at least three independent experiments. c Comparison of the mRNA levels from HAA1 and selected Haa1-regulated genes assessed in wild-type cells incubated in basal medium (white bars), or exposed to formic acid (30 mM) for 30 min (diagonal stripes bars) and in haa1Δ cells in cultivated in those same conditions (grey and black bars, respectively). The bars represent the average values of at least three independent experiments, and the error bars the associated standard deviation