What feature of bacteria allows for unique motility in spirochetes?

The unique motility of spirochetes is primarily attributed to their corkscrew shape. This distinctive morphology enables them to move in a rotary or corkscrew motion. As they twist and coil, spirochetes can navigate through viscous environments, such as mucus or tissue fluids, which is an advantage for their survival and pathogenicity.

While flagella are commonly associated with motility in many bacteria, spirochetes have a specialized arrangement of flagella known as axial filaments or endoflagella, which are located in the periplasmic space. This arrangement contributes to their corkscrew movement but is not the shape itself that facilitates the unique motility. Pseudopodia are extensions that some other cells, like amoebae, use for movement, and they do not apply to spirochetes. Cell wall composition, while important for overall structure and protection, does not directly influence how spirochetes move. Thus, it is the corkscrew shape that is fundamental to the distinctive motility of spirochetes.