FIG 1.

Stress response phenotypes of the sre1Δ and rim101Δ mutant strains. (A) Four independent sre1Δ mutant strains were serially diluted onto YPD medium and YPD pH 4 to 8. Growth was compared to wild type (WT) and a rim101Δ mutant known to have alkaline pH sensitivity. Growth was assessed after 3 days. sre1Δ #1 (HEB5) is shown for all subsequent phenotyping and analysis. (B) The sre1Δ and rim101Δ mutant strains are unable to grow at increasing pH levels on minimal medium (YNB). Strains were spotted in serial dilutions onto YNB medium buffered to pH 4.5 to 8.5, and growth was compared to WT after 3 days. (C) The sre1Δ and rim101Δ mutant strains display distinct and overlapping phenotypes to cell stressors. Strains were serially diluted and spotted to either YPD, YPD plus 1.5 M NaCl, YPD plus 0.5% Congo red, YPD plus 1 mg/ml caffeine, or YPD plus 0.03% SDS. Growth was compared to WT and assessed after 3 days. (D) The sre1Δ mutant strain displays a growth defect in response to hypoxia-mimicking growth conditions (7 mM CoCl₂). Strains were spotted in serial dilutions onto YPD at 30°C and YES plus 7 mM CoCl₂ at 30°C. Growth was assessed after 3 days and compared to WT and the rim101Δ mutant. (E) The sre1Δ mutant strain does not have the same capsule deficiency as the rim101Δ mutant strain. Strains were incubated in CO₂-independent medium for 3 days before imaging using India ink exclusion counterstaining. Capsule is noted as a halo of clearing around the yeast cells.