Question

While investigating a newly discovered Gram-negative bacterium, you find that when the bacteria die, the host experiences severe fever and inflammation. You suspect that the bacterium has __________ in its outer wall membrane.

A). exotoxin

B). coagulase

C). lipid A

D). M protein

Answer 1

Answer: Lipid A

The lipopolysaccharides (LPSs) of the outer membrane of Gram-negative bacteria has three main components. These are namely, (1) lipid A, (2) the core polysaccharide, and (3) the O side chain. Lipid A consists of two sugar derivatives of glucosamine which have fatty acids and phosphate molecules attached to them. The Lipid A part of the LPS of Gram-negative bacteria is a toxin in nature. Presence of lipid A in LPS allows it to act as endotoxin. Upon entry into the bloodstream of the host cell, lipid A causes the immune responses such as inflammation.