FIG 4.

Effect of disinfectants on biofilm-associated bacteria and nucleic acid levels. Cu (A and C) and PVC (B and D) drinking water biofilms, colonized with LpP1s1, were treated with free chlorine (A and B) or monochloramine (C and D). Biofilms were analyzed for LpP1s1 and HPC CFU (shown as bars with corresponding units on the left axis, log₁₀ CFU liter⁻¹) and total DNA and cDNA qPCR (shown as open symbols with connecting lines and units on the right axis, log₁₀ genomic copies [GC] liter⁻¹). Data (mean ± SD) are representative of two independent experiments with three replicates each (n = 6). a, P ≤ 0.001 compared to other biofilms at 5 min. b, P ≤ 0.05 compared to other biofilms at 15 min. c, P ≤ 0.01 compared to monochloramine Cu and PVC at 5 min. d, P ≤ 0.05 compared to free chlorine PVC and monochloramine Cu at 30 min. e, P ≤ 0.001 compared to monochloramine Cu and PVC at 5 min. f, P ≤ 0.01 compared to free chlorine Cu, monochloramine Cu, and PVC at 15 min. *, P ≤ 0.05; **, P ≤ 0.01.