Wild-type P. mirabilis and indicated mutants were suspended in either LB (A-D) or filter-sterilized pooled human urine (E) and distributed into 24-well plates. After a 20 hour incubated at 37°C under stationary conditions, biofilm biomass was quantified by crystal violet staining (A, C, D, and E) or by dilution and plating for determination of CFUs/ml (B). (C) LB was supplemented with 10 mM l-serine. (D) LB was supplemented with 10 mM alanine or pyruvate. Error bars represent mean ± SD for at least three independent experiments with at least 2 replicates each. *p<0.05, **p<0.01, ***p<0.001 by one-way ANOVA with Dunnett’s test for multiple comparison. ns=not significant.