True about the bacterial capsule is following except –
**Core Concept**
The bacterial capsule, also known as a slime layer or glycocalyx, is a complex polysaccharide structure surrounding certain bacteria, providing protection against environmental stressors, desiccation, and phagocytosis. The capsule is composed of repeating units of sugar molecules, such as polysaccharides or polypeptides, which are synthesized and secreted by the bacterial cell.
**Why the Correct Answer is Right**
The bacterial capsule plays a crucial role in the pathogenesis of encapsulated bacteria, such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis. The capsule helps these bacteria evade phagocytosis by preventing the attachment of complement proteins and opsonins, which are essential for the recognition and ingestion of pathogens by immune cells. The capsule also contributes to the virulence of these bacteria by protecting them from desiccation and environmental stressors.
**Why Each Wrong Option is Incorrect**
**Option A:** The bacterial capsule is composed of peptidoglycan, which is incorrect as the capsule is primarily composed of polysaccharides or polypeptides.
**Option B:** The capsule is not a virulence factor, which is incorrect as the capsule plays a significant role in the pathogenesis of encapsulated bacteria.
**Option C:** The capsule is not affected by beta-lactam antibiotics, which is incorrect as beta-lactam antibiotics can affect the synthesis of the capsule.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the presence of a bacterial capsule can be detected using the Quellung reaction, a serological test that utilizes specific antibodies to visualize the capsule.
**Correct Answer:** D.