FIG 3.

Addition of nitrate under biofilm-inducing conditions enhances motility of Salmonella. (A) Single colonies of wild-type S. Typhimurium inoculated in a 0.03% agar plate with or without 40 or 100 mM NaNO₃. Photographs were taken after incubation overnight at 28°C. Bacterial motility was determined by measuring the halo created by the bacteria as they swam. (B) Distance migrated by S. Typhimurium on plates with and without NaNO₃. (C) Western blot of extracts of S. Typhimurium incubated with or without NaNO₃ for flagellin. (D) Batch cultures of wild-type S. Typhimurium were grown shaking at 28°C for 72 h to induce biofilm production. NaNO₃ was added to each culture and shaken for an additional 4 h. (Left) Photographs demonstrating decreases in aggregation in the bottom of the flasks as NaNO₃ concentration increases. (Right) Sedimentation of aggregates collected from the flask and allowed to settle in Eppendorf tubes. (E) Fold change in csgA expression in biofilm-former populations from cultures supplemented with NaNO₃ determined by RT-PCR relative to the curli mutant.