The J5 mutant of E. coli lacks the enzyme uridine diphosphate glucose 4-epimerase and therefore produces an incomplete LPS, deficient in galactose and all the sugars distal to the central polymers. The J5 mutant has no O-specific chains and its endotoxin remains as the core LPS containing lipid A, N acetyl glucosamine, 2-keto-3-deoxyoctonate, heptose and glucose (a composition similar to that of the Rc strains of Salmonella).