Which structure is responsible for the mobility of many bacteria?

The structure primarily responsible for the mobility of many bacteria is flagella. Flagella are long, whip-like appendages that extend from the surface of bacterial cells and rotate like a propeller, allowing the bacteria to swim through liquid environments. This movement is essential for a variety of functions, including finding nutrients, escaping from harmful substances, and colonizing surfaces.

While pili and cilia may also be involved in bacterial movement, they serve different primary functions. Pili are mostly used for adherence to surfaces and for twitching motility, whereas cilia are primarily found in eukaryotic cells and are not typical in bacteria. Capsules, on the other hand, are protective structures that help bacteria evade the immune response but do not assist in mobility. Hence, flagella is the most prominent structure associated with the motility of many bacterial species.