Peritrichous bacteria make a run when
A.-the flagella turn clockwise and separate.
B.-the flagella turn counterclockwise and become bundled.
C.-the flagella turn counterclockwise and separate.
D. -the flagella turn clockwise and become bundled.
The Correct Answer and Explanation is:
The correct answer is:
B. – The flagella turn counterclockwise and become bundled.
Explanation:
Peritrichous bacteria are a type of motile bacteria with flagella distributed all around their cell surface. These flagella allow the bacteria to move in their environment through a process of coordinated motion. Their movement consists of alternating between two distinct types of movement: “runs” and “tumbles.”
- Running:
When peritrichous bacteria are in a “run,” they move in a straight line, typically toward or away from chemical stimuli in a process called chemotaxis. For a run to occur, the bacterial flagella must rotate in a coordinated fashion. In peritrichous bacteria, this happens when the flagella rotate counterclockwise. As they rotate in the same direction, the individual flagella bundle together, forming a coordinated and unified structure. This flagellar bundle acts like a propeller, allowing the bacterium to move forward in a smooth, directed manner. When the bacterium is moving in a favorable direction, it will continue to run for as long as it senses a favorable chemical gradient. - Tumbling:
When the flagella rotate clockwise, they lose coordination and separate from each other, causing the bacterium to tumble or change its direction randomly. This tumbling action reorients the cell so that when it resumes its run (with counterclockwise flagellar rotation), it can move in a new direction. Tumbling is essential for the bacterium to find optimal directions in response to environmental cues. - Chemotaxis and Adaptation:
Peritrichous bacteria use this run-and-tumble behavior to navigate their environment in response to chemical signals, a behavior known as chemotaxis. If moving toward a favorable stimulus, like a nutrient, they will extend their runs by minimizing tumbles. Conversely, if moving away from a harmful substance, they tumble more frequently to change direction.
In summary, for peritrichous bacteria to make a run, the flagella must rotate counterclockwise and form a bundled structure, allowing for smooth, linear movement. This coordinated flagellar motion is essential for efficient bacterial navigation and survival in various environments.