FIGURE 2.

ubi4Δ mutants exhibit a severe growth defect in zinc-deficient conditions. A and B, time course of wild-type (BY4741) and isogenic ubi4::KanMX4 mutant growth in zinc-replete (ZnR; A) or zinc-deficient (ZnD; B) medium (LZM with 100 or 1 μm added zinc, respectively). Cultures were inoculated with log phase cells to a starting A₆₀₀ of 0.01, and culture densities were recorded at the indicated times. C, effect of varying zinc concentration on growth of wild-type and ubi4Δ strains. Cultures were inoculated as described for A, and cell densities were measured after 48-h incubation. D, log phase cultures of wild-type and ubi4Δ mutant cells in zinc-replete medium were used to inoculate zinc-deficient medium. Cell viability was monitored over time by plating aliquots on YPD plates and counting colony-forming units following 2 days of incubation. E, the ubi4Δ growth defect in zinc-deficient medium is rescued specifically by zinc. Aliquots of LZM + 1 μm added zinc were supplemented with 100 μm ZnCl₂, FeCl₃, CuCl₂, MnCl₂, or CoCl₂ and inoculated with wild-type or ubi4Δ cells as described for A. Control (C) indicates LZM + 1 μm ZnCl₂ with no additional metal supplement. Cell densities were measured after 48 h. F, a ubi4Δ mutant was not hypersensitive to copper or iron deficiency. Aliquots of YPD were supplemented with 100 μm copper chelator bathocuproine disulfonic acid (BCS) or iron chelator bathophenanthroline disulfonate (BPS) with or without 100 μm added CuCl₂ or FeCl₃ and inoculated with wild-type or ubi4Δ cells as described for A. Control (C) indicates YPD with no additional metal or chelator supplement. Cultures were grown for 24 h, and cell densities were recorded. For all panels, data points represent averages of three independent cultures, and error bars denote ±1 S.D.