Which term describes hair-like structures that assist bacteria in attachment and motility?

The term that describes hair-like structures assisting bacteria in attachment and motility is pili. Pili are slender, thread-like appendages found on the surface of many bacteria. They play a crucial role in adherence to surfaces, which is essential for colonization and infection in various environments. These structures can also be involved in motility through twitching, allowing bacteria to move across surfaces.

In addition to pili, bacteria may utilize other structures for motility. Flagella are long, whip-like appendages that provide propulsion in liquid environments, allowing bacteria to swim. Cilia are similar structures found in eukaryotic cells, mainly involved in movement and feeding rather than bacterial attachment or motility. The cytoskeleton is a network of fibers that provides structure and support within a cell but does not directly aid in motility or attachment in the context of bacteria. Thus, pili are specifically suited to the roles described in the question.