Unique genetic basis of the distinct antibiotic potency of high acetic acid production in the probiotic yeast Saccharomyces cerevisiae var. boulardii

Sequence comparison of selected regions in Sdh1 from S. boulardii and S. cerevisiae and identification of the causative mutation. (A) Alignment of the Sdh1 amino acid sequence in regions 181–206 and 313–321 of the S. boulardii strains and of S. cerevisiae S288c. (B) Alignment of the corresponding Sdh1 sequence of S. boulardii SBERH6 and 18 additional S. cerevisiae strains. (C) Alignment of the corresponding Sdh1 sequence of two additional S. boulardii strains. The two positions, 202 and 317, with amino acid substitutions, are indicated with black arrows while substitute amino acid residues are in red. (D) Accumulation of acetic acid as a function of time by SBERH6 (•) and by SBERH6 strains with sdh1 replaced by SDH1^Y202H,Y317F (□), SDH1^Y317F (▴), or sdh1^Y202H (◊). (E) Accumulation of acetic acid as a function of time by Sb.P (•) and by Sb.P strains with the two copies of sdh1 replaced by SDH1^Y202H,Y317F (▿) or sdh1Δ (□). Results are the means of three biological replicates for each time-point. Error bars show standard deviation at each time-point.