Figure 3

Optimization of bacterial test volume on copper surfaces. ~1 × 10⁷ cells of E. coli Cu biosensor (a,c,e) or constitutively bioluminescent E. coli (b,d,f) in 25, 50 or 75 µL was placed onto 1 × 1 cm C11000 surfaces. Bacterial bioluminescence was registered during 60 min (a,b). The concentration of released copper from C11000 surfaces during 60 min in 25, 50 or 75 µL (indicated with arrows) was compared with standard response curve of the Cu sensor strain and constitutively bioluminescent strain (c,d). The number of viable cells in 25, 50 or 75 µL Cu biosensor or constitutively bioluminescent E. coli strain on C11000 surfaces after 60 min (e and f). Significant differences in viable counts from control value based on two-way analysis of variance (ANOVA) and Bonferroni’s multiple comparisons test are marked p < 0.1(.); p < 0.05(*); p < 0.01(**); p < 0.001(***); p < 0.0001(****). Solid red dotted line designates the background luminescence of E. coli Cu biosensor or constitutively bioluminescent E. coli; dotted red line designates significant increase (E. coli Cu biosensor) or decrease (constitutively bioluminescent E. coli) of bioluminescence. Mean and standard deviation of three replicates are shown.