What is the main function of the bacterial capsule?

The main function of the bacterial capsule is to provide protection from phagocytosis. The capsule is a thick, often sticky layer surrounding the bacterial cell wall, composed mainly of polysaccharides. This structure serves as a defense mechanism, making it more difficult for immune cells, like macrophages and neutrophils, to engulf and destroy the bacteria.

When bacteria possess a capsule, they can evade the host's immune response more effectively. The capsule hinders the adherence of immune cells and can also disguise the bacteria from being recognized as foreign invaders. Additionally, some capsules can help prevent desiccation and contribute to adherence to surfaces, but the primary and most well-studied role is indeed the ability to protect against phagocytosis.

Regarding the other options, energy storage typically involves structures like granules or lipid droplets, transport of nutrients is facilitated by various mechanisms and proteins embedded in the membrane and cell wall, and protein synthesis is carried out by ribosomes within the cytoplasm. These functions do not align with the protective role of the capsule.