On the Serological Specificity of the Escherichia coli O8 and O9 Antigens

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Abstract
The O8- and O9-specific lipopolysaccharides of E. coli lost their serological activity during liberation of the polysaccharide moieties (.alpha.-mannans) by mild acid hydrolysis, as tested by passive hemagglutination and hemagglutination inhibition. The serological activities and specificities were restored by substitution of the polysaccharides with 1 to 2 stearoyl groups/polysaccharide chain. The mannans obtained by biosynthesis in vitro were serologically active only when bound to the membrane-associated hydrophobic carrier molecule. Liberation of the polysaccharides from the carrier by treatment with aqueous phenol resulted in loss of the serological activity. The O8- and O9-specific mannans of E. coli are thus serologically active when they are part of an amphiphilic molecule and not as free polysaccharides.