Structure and polymorphic transformation of flagellar filaments. (a) Single flagellin monomer and arrangement of the monomers in the filament . Reprinted with permission from ref. 20, Copyright © 2006, Elsevier. (b) Bacterial flagellar filament polymorphic forms, shown in a curvature vs. twist plot. There are two straight forms, L (Left) and R (Right), and 10 helical forms. Of the named helical forms, normal and coiled are left-handed and the others are right-handed [21, 22]. Reprinted with permission from ref. 21, Copyright © 1998, Elsevier.