PolyP levels of stationary phase cells exposed to copper. (A) Cells of the indicated strains grown in MT + P for 48 h were exposed to increasing copper concentrations for 1 h. After incubations, polyP was quantified as described in Methods using DAPI fluorescence. (B) Time-course of polyP degradation in 48 h MT + P WT cells incubated with 0.25 mM Cu2+. Data are expressed as average ± SD of five independent experiments. DAPI emission was undetectable in cell free controls with or without copper addition.