Figure 6.

Δmpr1 cells are not sensitive to oxidative stress. (A) Wild-type (PR109), Δspc1 (KS1366), and Δmpr1 (CA288) cells were grown to midlog phase in YES medium at 30°C, and H₂O₂ was added at concentrations of 0, 1, and 2 mM. After 1 h of incubation at 30°C, cells were washed, diluted, and plated on YES agar medium. The survival of each strain was evaluated in terms of its colony-forming ability after 3 d of incubation at 30°C. Results from an average of three independent experiments are shown. (B) Oxidative stress–induced expression of the catalase gene, ctt1⁺, in Δmpr1 cells. The strains used in A were treated with 0.3 mM H₂O₂ in YES medium, and aliquots of cells were harvested at the indicated times for Northern hybridization analysis of the ctt1⁺ mRNA. The leu1⁺ probe served as a control. ctt1⁺ expression was strongly induced in Δmpr1 cells but was not detectable in Δspc1 cells.