(A) Effect
of coumarin on the biofilm formation of C. violaceum 12472, P. aeruginosa PAO1, and S. marcescens MTCC 97.
Different letters above the error bars represent different significance
groups by the Tukey test at p-value = 0.05. Data
are represented as mean values of triplicate readings, and bar is
standard deviation. The combined df and F values for biofilm inhibition of P. aeruginosa are 5 and 155.128, respectively. The combined df and F values for biofilm inhibition of S. marcescens are 5 and 171.195, respectively. The
combined df and F values for biofilm
inhibition of C. violaceum are 5 and
226.252, respectively. (B) Scanning electron microscopic images of P. aeruginosa PAO1 and S. marcescens MTCC 97 biofilms in the absence and presence of sub-MIC (250 μg/mL)
coumarin.