Fig 4.

Microscopic assay of membrane integrity following exposure to a 99.90% copper surface. E. coli strain ATCC 23724 was grown, harvested, and exposed to 99.90% copper (C11000) coupons, as described for Fig. 2. At the indicated times of exposure, the cells were washed from the coupon surface with 100 μl of 0.85% NaCl and prepared for the Live/Dead BacLight assay as described by the manufacturer (Invitrogen). Cells were observed using a Zeiss fluorescece Axioscope and an AxoCam ICm1 camera. The panels, from left to right, were viewed with phase-contrast illumination, a FITC filter (green), and a rhodamine filter (Rho; red). Total magnification used was 1,000× with oil immersion.