The structure of prokaryotes which is involved in attachment:

Explanation

Pili are hollow, nonhelical, filamentous appendages. They are primarily involved in a mating process between cells called conjugation. It helps the bacteria to stick to each other and to surfaces such as rocks in the flowing streams or to the lining of human intestines. Flagella helps with the motility of the bacteria while cilia are not present in prokaryotic cells. The cytoplasm also helps in the transport of material by cyclosis, the movement of cytoplasm.