Which of the following bacterial structures is necessary for chemotaxis?

• A. Flagellum
• B. Ribosome
• C. Plasmid
• D. Capsule

Answer: (A)

Verified step by step guidance

1. Understand the concept of chemotaxis: Chemotaxis is the movement of an organism in response to a chemical stimulus, typically moving toward nutrients or away from harmful substances.
2. Identify the bacterial structures listed: Flagellum, Ribosome, Plasmid, and Capsule, and recall their primary functions.
3. Recall that the flagellum is a whip-like appendage that enables bacterial motility, allowing the bacterium to move through its environment.
4. Recognize that ribosomes are involved in protein synthesis, plasmids carry extra genetic information, and capsules provide protection, but none of these directly enable movement.
5. Conclude that since chemotaxis requires movement toward or away from chemicals, the bacterial structure necessary for chemotaxis is the flagellum.