Which statement best describes endotoxin in bacterial physiology?

• A. Produced by living bacteria and released upon active secretion
• B. Released from the cell wall of dead bacteria
• C. A protein toxin that damages host tissues
• D. A polysaccharide component of the capsule

Answer: (B)

Endotoxins are lipopolysaccharide (LPS) components of the outer membrane of Gram-negative bacteria. Their toxic effects come from lipid A, but they are not actively secreted by living cells. They are released mainly when the bacteria die and the cell wall disintegrates, spreading LPS into the surrounding environment. This is in contrast to exotoxins, which are protein toxins actively secreted by bacteria, and to polysaccharide capsule components, which are separate from the LPS in the outer membrane. So the idea that endotoxin is released from the cell wall of dead bacteria best captures how endotoxins exist and become hazardous.