Lipid a component of Salmonella typhimurium carrying the derepressed Col Ib plasmids.

The structure of the lipid A from S. typhimurium harboring the derepressed plasmids Col Ib is very similar: i, 1,4'-bis-phosphorylated-beta-1',6-linked glucosamine disaccharide forms a backbone of the lipid; ii, lipid preparations contain four residues of 3-hydroxytetradecanoic acid at positions C3, C3' and the amide linked at C2, C2' and two free hydroxyl groups at positions C4 and C6'. Differences concern: i, substitution of phosphoryl groups by 4-amino-4-deoxy-L-arabinopyranose and phosphorylethanolamine in S. typhimurium with Col Ib plasmids; ii, the degree of acylation of hydroxyl groups of 3-hydroxytetradecanoic acid by myristic, lauric and palmatic acids; iii, presence of tridecanoic acid bound to hydroxyl of 3-hydroxy-tetradecanate residue in S. typhimurium with Col Ibdrd2 plasmid. Lipopolysaccharides from the plasmid mutant strains express several times higher lethal toxicity in chick embryos compared to lipopolysaccharides from the strain with the wild type Col Ib.