What structures make bacteria movable?

Bacteria are primarily made movable by structures known as flagella and cilia. Flagella are long, whip-like appendages that can rotate, providing the bacteria with the capability to swim through liquid environments. They often exist in various arrangements on the bacterial surface and play a critical role in the locomotion of many bacterial species.

Cilia, while more common in eukaryotic cells, can also be considered in the context of certain bacteria that have similar structures. These small, hair-like projections can help in movement by beating in coordinated waves, assisting the organism in navigating its environment.

The other options refer to structures that either do not exist in bacteria or are not applicable in terms of bacterial motility. Fins and legs are associated with aquatic and terrestrial animals, while wings and tails imply features of more complex multicellular organisms. Filaments and spikes may appear in certain contexts but do not provide the same function or relevance in bacterial mobility as flagella and cilia do.