What are hollow tubes used to move cells or exchange DNA between bacteria by conjugation?

• A. Capsule
• B. Flagella
• C. Pili
• D. Endospore

Answer: (C)

Hollow tubes that enable transfer of DNA between bacteria during conjugation are sex pili. These long, tube-like structures form a temporary bridge between donor and recipient cells, creating a channel through which a DNA plasmid—typically the F factor—can pass from the donor to the recipient. The recipient then uses its machinery to replicate the transferred DNA and form a complete plasmid. This distinguishes them from other surface features: a capsule is a protective polysaccharide layer, not a transfer channel; flagella are used for movement; and endospores are dormant survival structures. Some bacteria have fimbriae for attachment, but they don’t function as the hollow transfer conduit used in conjugation.