Figure 3. Ammonium,when present in the culture medium,impaired the consumption of theauxotrophy-complementing amino acids.

Leucine, lysine and histidine consumption of S. cerevisiae BY4742 cultured in SD media buffered to pH 3.4 with 2% (A and B) or 0.5% (C and D) glucose, supplemented with: high (A and C) and low (B and D) concentrations of auxotrophy-complementing amino acids (HAA and LAA, respectively), and with (w/) or without (w/o) NH₄⁺ [0.5%, (NH₄)₂SO₄]. Day -3 represents the day of culture inoculation and day zero represents the beginning of aging experiments. *(Peak values below detection limit ≈ 0). Values are means ± SEM (n=3).