FIG 2.

The bead movement in the biofilm is predominantly diffusive (Brownian motion). The following biofilms were grown on coverslips: E. faecalis (A), S. Typhimurium (C), E. coli (E), and isogenic curli mutants (D and F), and E. faecalis was grown in an optical-bottom 96-well plate (B). The evolution of the MSD over the course of each trajectory was calculated, and a quadratic least-squares fitting function used to determine if the average movement pattern of the beads was linear (red line), which would indicate movement by diffusive Brownian motion. (G) Example of elliptical bead movement observed in E. coli and S. Typhimurium biofilms taken from one frame of the E. coli 4D biofilm assay. (H) Example of large changes in bead patterns between frames taken from E. faecalis optical-bottom-well biofilm frame 3 and frame 4. Note that the biofilm itself also has some flowing movement (Video S2), giving the optical illusion of these frames not being in the same orientation.