Final answer:
Type IV bacteria have twitching motility due to the presence of type IV pili, which are thin, hair-like appendages on the surface of the bacteria.
Step-by-step explanation:
Type IV bacteria have twitching motility due to the presence of type IV pili, which are thin, hair-like appendages on the surface of the bacteria.
These pili extend and retract rapidly, allowing the bacteria to pull themselves forward like a grappling hook. By attaching to surfaces and contracting, the bacteria can move back and forth.
For example, the bacterium Pseudomonas aeruginosa uses twitching motility to move along solid surfaces, such as the lining of the respiratory tract during infection.