FIGURE 4.

Level of oxidative stress within the E. coli biofilm under both anaerobic (A–C) and aerobic (B–D) conditions. Data are referred to biofilm grown for 96 h in presence and absence of AgNPs (A,B) and to a 72-old established biofilm grown in absence of AgNPs and further treated with AgNPs for 24 h (C,D). Data represent the means ± SD of three independent measurements. According to post hoc analysis (Tukey’s HSD, p < 0.05), means sharing the same letter are not significantly different from each other and means sharing • showed significant difference in respect to control.