Question

The capsule is most advantageous to a bacterium because it
(a)Allows bacteria to hide from the host immune system
(b)Allows bacteria to attach to the surface
(c)Prevents it from desiccation
(d)Provides means of locomotion

Answer 1

The bacterial capsule is a large structure that is a characteristic of many bacteria. It is generally a layer of polysaccharide that lies outside the cell envelope and is thus deemed part of the outer envelope of a bacterial cell. It is a well-organized layer and does not easily get washed off, therefore it can be the cause of various diseases.

Complete answer:
The capsule assists the bacteria to adhere to surfaces, camouflages the bacteria from the immune system by mimicking the host tissues, and makes the bacteria resistant to complement invasiveness. It also protects cells from drying and toxic metabolites in the environment (heavy metal ions and free radicals).
Additionally, the capsule also enables the bacteria to become resistant to the bactericidal action of complement and serum antibodies and also acts as a diffusion barrier against antibiotics and contributes toward resistance mechanisms.

Additional information:
Many cells that are bacterial, secrete some extracellular material in the form of a capsule or a slime layer. A slime layer is another structure that is loosely associated with the bacterium cell body and can be easily washed off, whereas a capsule is attached tightly to the bacterium and has definite boundaries. Capsules can be viewed under a simple microscope by placing the cells in a suspension of India ink. The capsules eliminate the ink and appear as clear halos surrounding the bacterial cells. Capsules are most usually polymers of simple sugars or polysaccharides, although the exception includes the capsule of Bacillus anthracis is made of polyglutamic acid. Capsules are also capable of protecting a bacterial cell from ingestion and destruction by white blood cells (phagocytosis).

So, the correct answer is allowed bacteria to hide from the host immune system.

Notes: In addition to the various roles performed by capsules of bacteria, they are anti-phagocytic also. They restrict the ability of phagocytes to engulf the bacteria. The smooth nature and negative charge of the capsule stop the phagocyte from adhering to and engulfing the bacterial cell.