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The filament of the bacterial is of variable length (typically 5
to 10 mm) but has a constant diameter of about 20 nm throughout its length (BNID 100096).The bacterial flagellum differs from the eukaryotic flagellum in several regards: (i) the bacterial
flagellar filament, ca. 20 nm in diameter, consists of subunits of just one protein, whereas the eukaryotic
flagellum has a complex architecture and is much thicker, ca. 200 nm in diameter (ii) the filament does no
chemomechanical work but is passively driven by a motor at its base (iii) the mechanism is one of
rotation (8, 173), not bending (and hence the term 'flagellum,' meaning 'whip,' is misleading) (iv) the
motor can operate in either the counterclockwise (CCW) or clockwise (CW) direction (173) (i.e., it
possesses a switch) and (v) the energy source is the transmembrane proton potential (proton motive
force) (139), not ATP (121). (Numbers in parentheses refer to literature cited in Reference). |