FIG. 4.

(A) Schematic showing local coordinates for boxes on S-layer surface. Local coordinates are defined as follows: V₁ is tangential to the bacterium surface and follows one of the S-layer unit cell axes, n is normal to the surface following the p6 axis, and V₂ is a vector tangential to the surface resulting from the cross product of n|Ax × V₁. (B and C) Single dip (B) and double dip (C). The profiles are the result of adding intensity values along V₁ and V₂ in a single subtomogram. In the profiles we can see the inner membrane dip at 4 nm, the OM dip at 35 nm, and the S-layer dip between 50 nm and 65 nm. These profiles help classify each subtomogram into a single or double S layer for subtomogram averaging. The zero point in panels B and C was set arbitrarily to be able to display the main three features of the C. crescentus cell wall: OM, inner membrane, and S layer.