FIGURE 1. Comparison of the susceptibility to SO₂ of the Saccharomyces cerevisiae BY4741 parental strain and the deletion mutants Δmsn2, Δmsn4, Δhaa1 and Δcom2 by spot assays (A) or by cultivation in MMB liquid medium (pH 3.5) (▪) or in this medium supplemented with 0.5 mM of SO2 (□) (B). In (A) the cells used to prepare the spots were grown in MMB liquid medium until mid-exponential phase and then inoculated (at an OD of 0.05) in MMB (pH 3.5) agarized medium supplemented with the indicated concentrations of SO2. Lanes (b) and (c) are, respectively, 1:5 and 1:10 dilutions of the suspension used in lane (a). In (B) growth was followed by measuring culture OD₆₀₀ and the concentration of viable cells was assessed as the number of colony forming units per ml of cell culture (CFU ml-1). All the results presented are representative of at least three independent experiments that gave the same pattern of results.