Figure 4.

Synthetic lethality imposed by MPA causes retention of the survival plasmid. (A) Cells were maintained in 96-well microplates and hygromycin B was removed and replaced with medium containing 35 μM guanine and MPA in serial dilutions starting with 25 μg/mL. Microplates were read after 2 wk. (B) Cells in 96-well microplates were maintained over the entire time period in either medium with 35 μM guanine and 12.5 μg/mL MPA (rectangles) or in guanine-supplemented medium alone (triangles). Plate reading and data representation are as in Fig. 3.