What is the name of the hair-like bacterial structure used for attachment and conjugation? It is a pilus.
A pilus is a protein-based, hair-like appendage extending from the surface of many bacteria and some archaea. The plural is pili, and the structures are built mainly from repeating pilin proteins. Different pili perform different jobs, so “pilus” is a broad structural term rather than the name of only one specialized organelle.
Attachment pili, often called fimbriae, help bacteria adhere to surfaces, host tissues, or other bacterial cells. This attachment is important in colonization and biofilm formation. Conjugative pili, sometimes called sex pili, connect a donor cell to a recipient during bacterial conjugation. They help establish contact so genetic material—often a plasmid—can move between cells.
Pili are easy to confuse with flagella. Flagella are generally longer propulsion structures used for swimming, whereas pili are commonly associated with adhesion, DNA transfer, or twitching movement. Not every pilus transfers DNA, and conjugation also requires additional proteins that form the transfer machinery. The classic F pilus of Escherichia coli is the best-known example of a conjugative pilus.