Tailed bacteriophage is ______. 

The correct answer is Motile on bacterial surface.

Key Points

• Tailed bacteriophages are a type of virus that infects bacteria.
• They are characterized by their unique morphology, which includes a head (capsid) and a tail structure.
• The tail structure of these bacteriophages enables them to attach to specific receptor sites on the bacterial cell surface. This attachment is crucial for the bacteriophage to inject its genetic material into the host cell.
• While tailed bacteriophages do not exhibit motility in the traditional sense, as they cannot independently move, they can "move" across the bacterial surface by attaching to and detaching from different receptor sites, seeking a suitable entry point for infection.
• This "motility" on the bacterial surface is facilitated by the interactions between the bacteriophage's tail fibers and the bacterial cell's surface receptors, rather than by any sort of locomotion or propulsive movement.