(a) Synechococcus (strain WH8113) Crystalline outer surface of the surface layer (S) revealed where ambient ice is broken away. Arrowhead indicates fiber of 5 nm thickness that arises from cell membrane and extends to higher layers. Scale bar, 50 nm. (b) Synechococcus (strain WH8113) Patch of crystalline outer surface near fracture plane revealed by etching ambient ice. Since the bacterial surface is perpendicular to the line of sight, we used this image to measure the lattice arrangement: rhomboid with spacing ∼ 12 nm and obtuse angle ∼ 110°. Scale bar, 50 nm.