Figure 1: (a) Inhibition of bioluminescence (% of the control) in bioluminescent Escherichia coli in time and (b) induction of bioluminescence in Ag+-induced Escherichia coli in time upon exposure to different nominal concentrations of Ag nanowires (concentrations shown on the graphs). Note that the significant induction of Ag+-induced E. coli was observed only since 120 min of exposure and the induction increased with time. 240 min incubation was chosen for further experiments as this time resulted in highly significant induction, and the signal was easily distinguishable from the background (not induced) bioluminescence. Data represent mean ± standard deviation of three experiments. Negative inhibition values in (a) indicate small increase of bacterial bioluminescence at relatively low concentrations of Ag NWs, likely due to the hormesis effect [28].