Figure 2. Effect of carbon sources on chronological aging and stress response.

(A) Chronological survival of wild type (DBY746) cells in different media. Day 3 cells were washed and transferred to MES buffer in the presence of different carbon sources at the indicated concentrations. All media were adjusted to the same pH of the control (buffer only). (B) Stress resistance assay of wild type strain (DBY746) 24 hours after the switch to various buffers. Cells were heated for 100 min at 55°C or treated with 70mM H₂O₂ for 30min. A representative experiment was shown. (C, D) LacZ reporter assay. Wild-type cells with chromosomally integrated STRE- or PDS-lacZ reporter genes were switched to buffer containing different carbon sources after three days of growth in standard SDC medium. The STRE-lacZ (C) and PDS-lacZ (D) activities were measured 8 h and 24 h after the switch. Data shown are mean ± SEM (n=3–4). (E, F) Wild type (DBY746) cells were transferred to 40mM MES buffer (pH 6, pH 4) supplemented with ethanol (0.8%) or acetic acid (50mM) after two days of growth in SDC medium. The STRE-lacZ (E) and PDS-lacZ (F) activities were measured 4, 8 and 24 h after the switch (n=3). Star denotes p<0.05, double stars denote p<0.01. (G, H) Wild type cells were grown in SDC medium under the standard condition with limited aeration (aluminum caps) or high aeration condition (loose plastic caps). Extracellular acetate and ethanol concentrations were measured every other day.