Fig. 7.

Effect of HU pre-exposure on cross-adaptation to caspofungin. Parental strain SC5314 was passaged daily for 7 days in YPD+HU (IC₅₀; 2.814 mg/ml) at 37 °C, washed, and growth was measured on either solid (A) or liquid (B) medium. (A) ∼1 × 10⁵ cells were plated on YPD plates (with or without CSP [100 ng/ml] as indicated) and incubated at 37 °C for 3 days. (B) Passaged cells (with or without HU from the pre-exposure period above) were plated on YPD at a cell density of ∼200 CFUs/plate and incubated at 37 °C for 24 h. From each plate, 94 colonies from the control YPD treatment (gray curves), and 94 colonies from the YPD+HU treatment (blue curves) were randomly selected and grown at 37 °C in YPD with or without CSP (100 ng/ml); parental strain without pre-exposure was also tested (red curves). Growth was measured as absorbance at 600 nm every 15 min. (C) Strains evolved for 7 days as above were analyzed by spot assays. Serial dilutions of cell suspension were spotted (3 µl/spot) on YPD plates supplemented with the indicated concentrations of HU or CSP and incubated at 37 °C for 48 h. Each condition was tested a minimum of three independent times. Growth is represented in a heat map comparing strains with or without Chr2 trisomy (Chr2x3, euploid, respectively), as described in methods.