Bacterial Flagellar Movement

Bacterial Structure
Part 1
Structure of Fimbriae or Pili
Functions of Fimbriae or Pili
Parts of Flagella
Bacterial Movement
Flagellar Movement
Spirochaetal Movement
Gliding Movement
Nucleoid (Nucleus)
Plasmids
Classes of Plasmids
Gene Pickup and Sex Factors
R Plasmids
Plasmids Conferring Pathogenecity to mammals
Col Plasmids
Degradative Plasmids
Mercury Resistance Plasmids
Tumor Inducing Plasmid in Agrobacterium Tumifaciens
Cryptic Plasmids
Staphylococcal Plasmids

Bacterial Flagellar Movement

	Bacterial Flagellar Movement - Flagellar may be arranged all over the bacterial cell surface (peritrichous), or at the ends (polar). Eukaryote flagella contain ATPase, and can exhibit independent movement. They generate plane waves originating either from the base or the tip. Bacterial f1agella on the other hand, consist of a single non enzymatic protein, and are, therefore, incapable of independent movement. In contrast to the planar eukaryote flagellum, the bacterial flagellum normally shows a left-handed helical structure. Helical waves were, therefore, presumed to be propagated from the base to the tip of the flagellum.
Different mechanisms were suggested for generating helical waves. According to one view, contractile fibres of flagellin are formed. Another view held that the basal body wobbles, generating a wave which passes down the flagellum.still another view held that the propagation of waves was caused by the dislocations in the arrangement of the flagellin molecules. These views, however, cannot explain reversal of the direction of swimming, or why there is no damping out of waves passing down the flagellum.
Doetsch (1966) suggested that the motility of the bacterial flagellum could result from the rotation of the rigid helix from the basal body. According to this view the flagellum acts as a propeller of a boat. In bacteria with polar flagella, the flagellum rotates anti-clockwise, while the cell rotates clockwise during normal movement. The clock-wise rotation of the cell is slower because of the viscous drag. The thrust generated propels the cell forward, with the flagellum trailing. Rotation of the flagellum in the anticlockwise direction causes the bacterial cell to move in the opposite direction, with the flagellum in front.
In bacteria with peritrichous flagella, a training bundle of flagella rotate in the anticlockwise direction, resulting in smooth forward swimming. Reversal of flagellar rotation results in rambling tumbling movement. The rigid bacterial cells of Spirilla have non-helical tufts of polar flagella. Cones of flagellar rotation at one or both ends of the cell cause rotation of the cell. Coordinated reversal of rotation of flagellar tufts results in movement in the opposite direction. The basal body of the flagellum appears to be the motor which causes rotation. In a model suggested by Berg (1975,' 76), the turning motion is generated between the M ring which is fixed to the flagellum and the S ring which is fixed to the cell wall. The M ring functions as a rotor and the S ring as a stator.
	The P and L rings are just bushings. Since the flagellum rotates both clockwise and counterclockwise, the basal body provides a universal joint which permits complete rotation of the hook and shaft. Energy is transformed into work in the basal body. The driving force is associated with local proton circulation. Movement of ions between the M and the S rings might power the flagellar motor. It is possible that the proton current turns the motor in some direct manner. The process might be powered by a high-energy intermediate. The power mechanism of bacterial flagella is different from that of eukaryote flagella, which are powered by ATP.

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