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Figure 7: Bactericidal effect of kaurenoic acid (KA). Cultured Streptococcus mutans was treated with KA and stained with LIVE/DEAD BacLight Bacterial Viability Kit. The stained bacteria were observed by confocal laser scanning microscopy. Treatment with KA decreased green-labeled living bacteria (SYTO 9 stain) and increased red-labeled dead bacteria (PI stain) in a dose dependent manner. (a) Control; (b) 1 μg/mL, (c) 2 μg/mL, (d) 3 μg/mL, and (e) 4 μg/mL of KA; and (f) positive control (0.1% NaF). Bar = 50 μM.