Isolated heterocysts of Anabaena variabilis synthesize envelope polysaccharide.

Isolated heterocysts, incubated for 1 h at 30 degrees C [14C]mannose, synthesize [14C]arabinose and [14C]glucose, and incorporate the three 14C-labeled sugars into their envelopes with glycosidic linkages characteristic of their envelope polysaccharide. In extracts of metabolic intermediates with hot 80% methanol, [14C]mannose is associated with the nucleotide GDP and [14C]glucose and [14C]arabinose with UDP. Chloroform/methanolic extracts of the heterocysts contain phosphoglycolipids in which 14C-labeled mannose, arabinose, and glucose are present. The lipids have the same as dolichol phosphate mannose under varying chromatographic conditions, RF and like polyisoprenol monophosphate glycolipids are stable to treatment with mild alkali but labile to mild acid hydrolysis. If bacitracin is added to the incubation mixture, 14C-labeled nucleotide sugars accumulate, but incorporation of 14C into envelope polysaccharide is greatly diminished. This observation supports the interpretation that polyisoprenol phosphoglycolipids are intermediates in the biosynthesis of this polysaccharide.