Fig. 1. Effect of nitrate on periodontal biofilm formation.

Real-time 7 or 12 h growth curves of in vitro periodontal plaque biofilms under different treatment conditions, namely (A) samples supplemented with or without 5 mM nitrate (n = 20), or (B) with or without 50 mM nitrate (n = 10). Biofilm formation is expressed as Cell Index (CI) as determined using impedance measurements. Standard deviations are shown at 30 min intervals. The error bars represent the standard deviation of the mean. Statistically significant differences (p-value < 0.05 according to Wilcoxon matched pairs signed-rank test) are marked by an asterisk (*). The addition of the Ra9 strain appeared to affect initial biofilm formation, but had no significant effect on the final biofilm quantity (Supplementary Fig. 1).