Mcgraw Hill Connect Microbiology Exam 1 Practice Test

Lipid polysaccharide pairs are a defining feature of the outer membrane found in Gram-negative bacteria. This complex, consisting of lipid A, a core polysaccharide, and an O-antigen, sits on the outer leaflet of the outer membrane and contributes to the cell’s barrier and endotoxin properties. Gram-positive bacteria, on the other hand, lack an outer membrane and instead have a thick peptidoglycan layer with teichoic acids, so they do not contain LPS. Therefore, lipopolysaccharides are characteristic of Gram-negative envelopes.