Lipopolysaccharide containing L-acofriose in the filamentous blue-green alga Anabaena variabilis.

For the first time, an O-antigenic lipopolysaccharide (LPS) has been isolated from a filamentous blue-green alga (Anabaena variabilis). It was extractable with phenol-water, resulting in extraction of the bulk of the LPS into the phenol phase. The polysaccharide moiety of this LPS consists of l-rhamnose, its 3-O-methyl ether l-acofriose, d-mannose, d-glucose, and d-galactose. l-Glycero-d-mannoheptose and 2-keto-3-deoxyoctonate, the two characteristic sugar components of enteric LPS, and phosphate groups are absent from the A. variabilis O antigen. The only amino sugar present is d-glucosamine. Three hydroxy fatty acids were identified, namely, beta-hydroxymyristic, beta-hydroxypalmitic and beta-hydroxystearic acids, in addition to palmitic and unidentified fatty acid. The LPS of A. variabilis is localized in the outermost cell wall layer and behaves like a bacterial O antigen in serological tests. The passive hemagglutination yielded high titers with isolated LPS (pretreated by heat or by alkali) and rabbit antisera prepared against living or heat-killed cells. The position of the precipitation arcs after immunoelectrophoresis of the O antigen indicates the lack of charged groups. The water phase of the phenol-water extract contains, in high yield, a glucose polymer. It is serologically inactive as shown by the passive hemagglutination test and by agar-gel precipitation.