FIGURE 3. (A) Comparison of the susceptibility towards SO₂ of the mutants devoid of the expression of genes whose transcription is activated in response to SO₂ in a Com2p-dependent manner. Cells of the parental strain (wt) and of the indicated deletion mutants were grown until mid-exponential phase in liquid MMB medium (at pH 3.5) and then used to inoculate the same basal medium either supplemented (open symbols) or not supplemented with 0.5 mM SO₂ (filled symbols) (at pH 3.5). Cells were batch cultured at 30ºC and growth was monitored based on OD_620nm. The growth curves presented are representative of at least three independent growth experiments. (B) Wild-type strain was challenged for 24h in MMB pH 3.5 without and/or with 0.5 mM SO₂ supplemented with 1 g/L of lysine.