What is the disease-causing part in a bacteria?

• A. The protein capsule
• B. The ribosome
• C. The flagellum
• D. The nucleoid

Answer: (A)

Bacteria cause disease in part because of protective outer layers that help them survive inside a host. The capsule is that outer cover, which can shield the bacteria from immune cells and prevent being engulfed and destroyed (phagocytosis). This makes infections easier to establish and sustain, so the capsule is the part most directly tied to disease-causing ability. The other structures have important roles—ribosomes build proteins, including normal ones needed by the cell; flagella help with movement; and the nucleoid contains the genetic material—but they don’t directly enable disease in the same way the capsule does.