A Gram-negative bacterium injects bacterial proteins directly into host cells using a specialized needle-like appendage to manipulate host cellular processes. This virulence mechanism is characteristic of which system?

✓ Correct Answer: Option C

The Type III secretion system (T3SS) is often called an 'injectisome.' It directly injects effector proteins from the bacterial cytoplasm into the host cell cytoplasm, bypassing the extracellular environment.