Characteristics of a bacterial capsule include which of the following?

Characteristics of a bacterial capsule include which of the following?

• A. It cannot be used for vaccine development.
• B. It is composed of peptidoglycan.
• C. It is what causes bacteria to stain as gram-negative.
• D. It is an important mechanism for protecting a bacterium against ingestion by PMNs.

Answer: (D)

Bacterial capsules are slim, polysaccharide-rich layers outside the cell wall that serve as an antiphagocytic shield. They help bacteria resist ingestion by PMNs by making it harder for these immune cells to recognize, bind, and engulf the bacteria, often by reducing opsonization and limiting complement deposition. This protection against phagocytosis is a major reason capsules contribute to virulence and a reason why they’re important targets for vaccine development (capsule polysaccharides can be used to induce protective antibody responses). Capsules are not made of peptidoglycan—the cell wall is. Their presence does not determine Gram staining, which depends on cell wall structure and thickness; both Gram-positive and Gram-negative bacteria can have capsules.

Bacterial capsules are slim, polysaccharide-rich layers outside the cell wall that serve as an antiphagocytic shield. They help bacteria resist ingestion by PMNs by making it harder for these immune cells to recognize, bind, and engulf the bacteria, often by reducing opsonization and limiting complement deposition. This protection against phagocytosis is a major reason capsules contribute to virulence and a reason why they’re important targets for vaccine development (capsule polysaccharides can be used to induce protective antibody responses).

Capsules are not made of peptidoglycan—the cell wall is. Their presence does not determine Gram staining, which depends on cell wall structure and thickness; both Gram-positive and Gram-negative bacteria can have capsules.