Rhamnolipids from Pseudomonas aeruginosa disperse the biofilms of sulfate-reducing bacteria

D. vulgaris biofilm dispersal by supernatants of P. aeruginosa PA14, its quorum sensing mutants, P. aeruginosa PAO1, B. subtilis, P. fluorescens, E. coli TG1, and homoserine lactones. (a) D. vulgaris biofilms were grown for 2 days in modified Baar’s media at 30？°C, and all of the supernatants were concentrated to 4× and contacted with D. vulgaris biofilms for 2？h. * indicates no dispersal. At least two independent cultures were used with three replicates for each culture, and the error bars indicate one standard deviation. (b) D. vulgaris biofilms were grown for 2 days in modified Baar’s medium at 30？°C, and supernatants were concentrated to 4× and contacted with D. vulgaris biofilms for 2？h. Rhamnolipid standards were added at 10？mM. Protease 1 (Savinase) at 0.024？U was used as a positive control. At least two independent cultures were used with three replicates for each culture, and the error bars indicate one standard deviation. (c) D. vulgaris was grown for 24？h to form biofilms in modified Baar’s medium. PA14 wild-type supernatants were used at 1× (so that the effect of the homoserine lactones could be more clearly discerned) with 50？μM of C4-HSL, 3oxoC12HSL, or DMF (negative control) added for 90？min. Savinase (protease) at 0.024？U was also used as a positive control with PBS buffer used as negative control for protease. Two independent cultures and three replicate wells for each condition were used. The error bar indicates one standard deviation. The symbols ** (P？<？0.01) indicate significant differences versus the PA14 supernatants？+？DMF control via one-way ANOV