VCDH Microbiology Practice Test

Endotoxins are associated with which bacterial feature?

Viral envelopes The thick peptidoglycan layer of Gram-positive bacteria The outer membrane of Gram-negative bacteria Fungal cell walls

Correct Answer:

The outer membrane of Gram-negative bacteria

Explanation:

Endotoxins come from the outer membrane of Gram-negative bacteria, specifically the lipopolysaccharide (LPS) layer. The toxic component, lipid A, can trigger strong inflammatory responses that lead to fever and septic shock. Endotoxins are not secreted toxins; they’re part of the cell envelope and are released mainly when bacteria die or lyse. Because Gram-negative bacteria have this outer membrane, they house endotoxins, whereas Gram-positive bacteria lack an outer membrane and rely on other cell-wall components and exotoxins. Viral envelopes and fungal cell walls are unrelated to bacterial endotoxins.

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