Gram Staining question

Question

Can Gram staining identify endotoxins?

If so, why do we use the LAL procedure to detect endotoxins?

Thank you

Answer 1

Gram Staining is a technique used to detect both gram-negative and gram-positive bacteria (microbes). If the microbe is gram negative, then there is a visual color change to red. If the bacteria is gram positive, then there will be a visual color change to purple. 

Endotoxin is a component of gram-negative bacteria’s cell wall. 

The LAL procedure is used due to the fact that the lysate from the blood cells of horseshoe crabs react with microbial endotoxins; if the microbe has endotoxins, then this test would result in the formation of a cloth (solid mass) or color change, indicating a positive test result (gram negative bacteria). A negative test result will not form a cloth, indicating that the bacteria has no endotoxins.