Run-and-tumble motion

Flagellum from a gram-negative bacterium (unlabelled)

Run-and-tumble motion

Run-and-tumble motion is a type of movement exhibited by certain microorganisms, particularly bacteria, as they navigate through their environment. This motion pattern involves alternating phases of running in a straight line and tumbling or changing direction abruptly. The mechanism behind run-and-tumble motion allows these microorganisms to effectively explore their surroundings in search of nutrients, avoid harmful substances, and locate optimal conditions for growth and reproduction.

Mechanism

During the "run" phase, the microorganism propels itself forward in a relatively straight path by rotating its flagella or other motility structures. This movement is typically driven by the generation of a directional force that pushes the cell in a specific direction. As the microorganism continues to run, it assesses its environment for favorable or unfavorable conditions.

When the microorganism detects a stimulus that triggers a change in direction, such as a gradient in nutrient concentration or a physical barrier, it enters the "tumble" phase. During tumbling, the microorganism halts its forward motion and reorients itself by changing the direction of its flagellar rotation. This abrupt change in direction allows the microorganism to explore a new path and respond to environmental cues effectively.

Significance

Run-and-tumble motion is a crucial behavior for many microorganisms, particularly bacteria, as it enables them to navigate complex and dynamic environments. By alternating between running and tumbling, these microorganisms can efficiently search for nutrients, locate optimal habitats, and avoid harmful substances. This movement strategy is essential for their survival, dispersal, and interactions with other organisms in their ecosystem.

Examples

One well-known example of a microorganism that exhibits run-and-tumble motion is Escherichia coli, a common bacterium found in the gastrointestinal tract of humans and other animals. E. coli uses its flagella to run in a straight line and tumble to change direction, allowing it to move towards nutrient sources and away from toxic substances.

Research

Scientists have studied run-and-tumble motion in microorganisms to gain insights into their behavior and ecological roles. Understanding how bacteria and other microorganisms navigate their environments can provide valuable information for various fields, including microbiology, ecology, and biotechnology.