FIG. 4.

Drug resistance profiles of S. cerevisiae WT and erg mutants determined by the spot assay (A) and the microtiter assay (B). (A) For the spot assay, the yeast cells were grown overnight on YNB plates at 30°C. The cells were then suspended in normal saline to an OD₆₀₀ of 0.01 (A₆₀₀). Five microliters of fivefold serial dilutions of each yeast culture was spotted onto YNB plates in the absence (control) and presence of the following drugs: 4-NQO (0.02 μg ml⁻¹), CYH (0.01 μg ml⁻¹), PHE (2 μg ml⁻¹), SMM (1 μg ml⁻¹), FLC (8 μg ml⁻¹), and MTX (1 μg ml⁻¹). Growth differences were recorded following incubation of the plates for 48 h at 30°C. Growth was not affected by the presence of the solvents used for the drugs (B) The microtiter assay (MIC₈₀) was done as described in Materials and Methods.