What structure helps the bacteria bacilli and spirilla move?

Bacilli and spirilla are types of bacteria characterized by their rod-shaped and spiral forms, respectively. The structure that aids in their movement is called flagella. Flagella are long, whip-like appendages that extend from the surface of the bacterial cell. They rotate or whip back and forth, allowing the bacteria to propel themselves through their environment.

The effectiveness of flagella in bacterial locomotion is crucial for survival, as it helps the bacteria to find nutrients, escape from harmful substances, and engage in behaviors that promote their growth and reproduction. Therefore, among the options provided, flagella is the correct choice because it directly relates to the movement of bacteria like bacilli and spirilla, enabling them to navigate through liquids or viscous environments efficiently.