Copper tolerance in stationary phase cells. Copper tolerance of 48 h MT or MT + P growing cells of the indicated strains (panels A-F) was determined after one-hour exposure with different copper concentrations. Serial dilutions of cells incubated without copper (control) or treated cultures were spotted in LB-agar plates. The last spot of each strip was loaded with 1/100000 dilution of original cultures. Data are representative of at least four independent experiments.