Movement with flagella

Bacterial movement in solution can be separate into two main actions that are: the run is where the bacterium moves in a straight line towards an attractant. If the attractant moves or disappears then the cell tumbles before starts another run.  Random tumbling is the only form of steering that bacteria have at their disposal. Depending on how the filaments are attached to the cell flagella are used in three main ways to achieve locomotion:

? Peritrichous: Flagella rotate anticlockwise and bundle together. This allows the bacterium to move forward. Clockwise rotation causes the flagella to unbundle and pushes the bacterium in every direction simultaneously.

? Polar: If the Bacterium has a reversible motor for its flagellum anticlockwise rotation causes a run.  Clockwise rotation can lead to either a run in the reverse direction or a tumble. If the flagellar motor can only rotate anticlockwise, then the cell can only reorientate itself through allowing and stopping Brownian motion to randomly knock it into a suitable position to move in another direction.

? Lipotrichous: Runs and tumbles occur in the similar way as for bacteria with peritrichous flagella.

Other types of movement

All prokaryotes appear to move under the light microscope as they are sufficiently small to be shaken through random bombardment of local molecules. Additionally, convection currents generated through the light source will appear to make nonmotile bacteria move slightly.  Although flagella are widespread via the Bacterial and Archaeal kingdoms other forms of locomotion have evolved. Several Bacteria have a gliding motility which allows flagella-free bacteria to move rapidly across surfaces. In the Cyanobacteria this gliding is achieved through the secretion of slime although the exact way in which this allows the Bacterium to move is poorly understood. Flavobacterium johnsoniae also glides but appears to achieve this through using cell wall proteins to grab onto the surface and haul the Bacterium along a few nanometers at a time.

The spirochetes exploit their helical morphology to generate a unique form of movement dependent on internalized flagella. These corkscrew-like cells have axial endoflagella or filaments located among the cell membrane and the cell wall. The rotation of these structures causes the whole cell to wriggle and rotate and motion results.