FIG 4.

Addition of nitrate alters the architecture of the mature biofilm. (A) 3D views of untreated and nitrate-treated wild-type S. Typhimurium biofilms. Biofilms were grown on round coverslips for 72 h at 28°C. The mature biofilms were washed and treated with 100 mM NaNO₃ for 1 or 4 h before staining with SYTO 9 (green) and imaged using confocal microscopy (63× oil magnification). (B) 3D surface plots were created of the 4-h time point, forming two distinct layers, a less compact upper layer (red particles) and a compact lower layer (green particles). (C) Quantification of 3D surface plots showing an increase in the number of particles in the upper layer (red particles).