Zn2+ disrupts cell metabolism and division. (A) The sensitivity of the parental strain, BY4741, transformed with the plasmid, YEp, was assessed using cultures grown in SD medium to mid-exponential phase. A sample was serially diluted by factors of 10, and stamped onto SD or YPD media supplemented with 0, 10 or 13 mM ZnSO4 or 13 mM ZnSO4 and 0.002% uracil as indicated. This montage was assembled from photographs taken after 4 d growth at 30°C. (B) The morphological responses to zinc were assayed by growing the parental strain in SD medium to exponential phase and then treating it with or without 13 mM ZnSO4 for 6 h at 30°C. Left parts show samples of the populations at that time, while right panels show cells exhibiting the most common phenotypes. The arrow points to a vacuolar inclusion that can be found in 54.0% ± 1.5% of the zinc-treated cells but in none of the untreated ones. (C) The effect of zinc on cell viability was assessed by growing the parental strain at 30°C in SD medium to exponential phase, diluting it in fresh SD medium and after 2 h (indicated by arrow), adding ZnSO4 to bring the culture to 13 mM. Samples were removed every 2 h, spread onto YPD agar and incubated for 2 d to count the number of colony-forming units. The left scale shows the average percent change (±SD) for 4 independent replicates. Solid line, untreated cells; broken line, Zn2+-treated ones. The right scale shows the percent of cells (±SD) at each time point that accumulated PI. Black bars, untreated cells; white bars, treated cells.