FIG 4.

Killing of Acinetobacter biofilms and planktonic cells by copper. AB5711 cultures were incubated statically overnight at 37°C in a 24-well tissue culture-treated plate to establish biofilms. The LB broth was removed and replaced with M9 medium containing the indicated concentration of CuSO₄. After 0, 6, or 24 h of additional incubation, bacteria from both the supernatant (planktonic) and the biofilm were serially diluted and plated for enumeration of CFU. Percent survival was calculated as the percentage of the bacteria present at time zero under each condition. Data are presented as mean and ranges for four biologically independent replicates. One-way ANOVA with Welch's correction followed by linear contrasts with Bonferroni adjustment was used to compare biofilm and planktonic cell percentages of survival at each concentration and time point. Statistically significant comparisons (P < 0.01) are indicated with asterisks.