Prokaryotic Flagellar Movement: Videos & Practice Problems

Prokaryotic organisms exhibit a unique form of movement known as motility, which refers to their ability to move independently. A specific type of motility, termed swimming motility or flagellar motility, is driven by the rotation of flagella. This process allows cells to navigate through their environment effectively.

Swimming motility occurs when the flagella rotate in a particular direction, propelling the cell forward. For instance, when a flagellum rotates counterclockwise, it enables the cell to swim. Conversely, if the flagellum rotates clockwise, the cell will cease its movement. This directional control of flagellar rotation is crucial for the swimming behavior of prokaryotic cells.

To illustrate this concept, consider a monotrichous bacterium, which possesses a single flagellum at one pole. The rotation of this flagellum determines the cell's movement. The counterclockwise rotation facilitates swimming, while a switch to clockwise rotation results in a halt in motion. Understanding this mechanism is fundamental to grasping how prokaryotic cells interact with their surroundings and navigate through various environments.

As we delve deeper into the study of prokaryotic flagellar movement, we will explore additional aspects and complexities of this fascinating topic.

Prokaryotic flagellar movement is characterized by a unique swimming pattern known as runs and tumbles. This method of motility allows cells to navigate their environment effectively. A run refers to a smooth, directed movement of the cell, which occurs when the flagella rotate in a coordinated manner, typically in a counterclockwise direction (CCW). In contrast, a tumble is an abrupt, random change in direction that happens when the flagella rotate clockwise (CW), resulting in a lack of net movement in any specific direction.

In the case of peritrichous bacteria, which have flagella distributed around their surface, the coordinated rotation of flagella enables the cell to swim forward during a run. When the flagella switch to a clockwise rotation, the cell tumbles, altering its direction. This cycle of runs and tumbles continues, allowing the cell to explore its surroundings.

Importantly, the movement of the flagella is powered by a proton motive force (PMF), which is generated by the flow of protons across the cell membrane. This energy source is crucial for the rotation of the flagella and, consequently, for the motility of prokaryotic cells.

Understanding the mechanics of runs and tumbles provides insight into how prokaryotic organisms navigate their environments, highlighting the intricate relationship between cellular structure and function.