Extracellular polysaccharides were isolated from the blue-green alga Anabaena flos-aquae strain A-37. The polysaccharides are composed of glucuronic acid, glucose, xylose, and ribose in a molar ratio of 1:88:39:3. The extracellular polysaccharides comprise about 40% of the total carbohydrate produced by this alga.Carbon utilization experiments revealed that only D-fructose could be substituted for carbon dioxide as a precursor of polysaccharides and cellular material.The extracellular polysaccharides are derived from water-soluble intracellular polysaccharides of the same composition.Fructose accumulates in stationary phase cells grown in CO2 and the presence of the enzymes fructose diphosphate phosphatase and fructose diphosphate aldolase was demonstrated. Tracer studies showed the presence of phosphorylated compounds common to the photosynthetic carbon reduction cycle and the glycolytic pathway.
A new ferredoxin-dependent carbon reduction cycle in a photosynthetic bacterium.