Chemical composition and biological properties of a lipopolysaccharide from Bacteroides intermedius

Endotoxin (lipopolysaccharide, LPS) from an oral strain of Bacteroides intermedius was isolated by phenol extraction and purified by ultracentrifugation and gel filtration. The preparation was essentially free from contaminating nucleic acid and protein. The LPS contained rhamnose, fucose, mannose, glucose, galactose, glucosamine, and an unidentified sugar (approximate molar ratios 9:1:6:3:1:7:2). Neither heptose nor 2-keto-3-deoxyoctonate was detected. The major fatty acids were 3-hydroxy-15-methylhexadecanoic acid and 3-hydroxyhexadecanoic acid. The LPS was homogeneous with regard to molecular size, and its polysaccharide chain appeared short compared to the E. coli 055 LPS which was used as reference. A molecular weight of approximately 7,800 was estimated from gas chromatography data and by gel filtration in the presence of sodium deoxycholate. The B. intermedius LPS demonstrated low potency in the Limulus amoebocyte lysate assay, and in the chick embryo and mouse lethality tests and gave negative response in the local Shwartzman reaction.