What is the primary function of the bacterial flagellum?

The primary function of the bacterial flagellum is motility, which refers to the ability of bacteria to move toward or away from environmental stimuli. The flagellum acts like a whip or propeller, allowing bacterial cells to navigate through liquid environments. This movement is essential for various processes, such as finding nutrients, escaping harmful substances, and colonizing new environments.

In addition to motility, the flagellum is also involved in certain communication processes between bacteria, influencing behaviors like biofilm formation and virulence. However, its main role remains to provide the means for movement, enabling bacteria to locate optimal conditions for growth and survival.

Other choices represent different functions that are not related to the primary role of the flagellum. For instance, photosynthesis is a process specific to certain types of plants and algae, not bacteria in general. Adhesion to surfaces is typically facilitated by structures like pili or fimbriae rather than flagella, and drug resistance is more related to cellular mechanisms and modifications that can occur in response to antibiotics rather than the mechanical function of motility provided by flagella.