What is the function of the bacterial capsule?

The bacterial capsule serves as a vital protective layer surrounding the bacterial cell wall. Its primary function is to shield the bacteria from the immune responses of the host, particularly phagocytosis, which is the process by which immune cells engulf and destroy pathogens. The capsule can inhibit the ability of phagocytes to recognize and ingest the bacteria, thereby enhancing the bacteria's survival in hostile environments, particularly those involving a host immune response.

Capsules are composed of polysaccharides and sometimes proteins, and their presence can significantly contribute to the virulence of certain bacterial species by allowing them to evade detection by the immune system. This ability to resist phagocytosis can lead to increased pathogenicity, making the organism more likely to cause disease.

While the other options might touch on different aspects of bacterial function or cellular structure, they do not accurately depict the primary role of the capsule. Bacterial reproduction is typically associated with binary fission rather than any external structure. Nutrient storage is more commonly facilitated by other intracellular mechanisms rather than a capsule. Movement in bacteria is generally enabled by structures like flagella, rather than a capsule, which is primarily a protective feature.