Inhibition of Biofilm Formation. The inhibitory effect ofhordenine on P. aeruginosa PAO1 biofilm formation was presentedin Figure 3. Treatment with hordenine at concentrationsof 0.75 and 1.0 mg mL−1 significantly reduced the formationof biofilms by 26% and 31%, respectively (Figure 3A). Afterhordenine treatment, planktonic cell survival was alsodetermined. Results showed that hordenine treatment (0.5 to1.0 mg mL−1) had no effect on the viability of planktonic cellscompared with that of the control (Figure 3B).