Fig. 1.

Dictyostelium proliferation in varying concentrations of phenylthiourea. Dictyostelium cells were grown in axenic medium over 168 hours in shaking suspension in the presence of phenylthiourea. (A) Phenylthiourea concentrations from 0.5–5 mM provided a range of inhibitory effects on cell growth; 5 mM was found to be toxic to cells. Growth rate determined between 66 and 114 hours revealed a significant (P<0.05) reduction between control conditions and both 1 mM and 2 mM phenylthiourea. (B) Secondary plot during log growth phase (66–114 hours; grey box in A) for 0.5–2 mM phenylthiourea showing the change in growth rate at each concentration to estimate a potency of inhibition (IC₅₀) of 1.95 mM. Data from A are presented as means ± s.e.m. of triplicate experiments.