Movie S1.

Pel is a major structural component of the biofilm stalk. In this 3D movie of a PBADpel 3-d biofilm stained with biomass stain (Syto62, green) and Pel-specific lectin (WFL, red), the image rotates about the z-axis initially showing both red and green channels, after which the green channel fades to accentuate columns of Pel in the biofilm stalk. Note how intertwined fibers or columns of Pel connect the surface to the top of the microcolony.