Fig 1.

E. coli survival and lipid peroxidation following exposure to different CuSO₄ concentrations in liquid medium. E. coli strain ATCC 23724 was grown at 37°C in LB medium to mid-log phase (OD₆₀₀, 0.3). At time zero, CuSO₄ was added to the culture to the indicated concentration, and incubation continued for the course of the experiment. (A) At the indicated time, cells were harvested by centrifugation from 100 ml of culture and resuspended in 200 μl of 0.85% NaCl. Survival, reported as the number of CFU, was determined by diluting culture samples in 0.85% NaCl and plating on LB agar. The error bars indicate standard deviations from three independent cultures for which titers were determined in duplicate. (B) CuSO₄ was added to the cultures to the indicated final concentration and harvested 60 min after the addition of CuSO₄, as described for panel A. The control (0) is the sample taken at time zero, prior to the addition of CuSO₄. Membrane lipid peroxidation products were determined as TBARS and are reported as nmoles MDA equivalents/10⁹ cells (see Materials and Methods). The error bars indicate standard deviations from three independent cultures assayed in duplicate.