Presence of a Sulfated Polysaccharide in the Extracellular Matrix Ofplatydorina Caudata(volvocales, Chlorophyta)1

Evidence for the presence of a sulfated polysaccharide component within the extracellular matrix ofPlatydorina caudataKofoid is presented. In situ staining with alcian blue and toluidine blue O indicates accumulation of a sulfated polysaccharide in the matrix. The entire matrix was readily solubilized by a hot aqueous extraction and a sulfated proteoglycan complex was isolated. Thin‐layer chromatography of hydrolysates and infrared analysis and chemical desulfation of the intact molecule indicate that the polysaccharide component is principally an arabinogalactan with ester‐linked sulfate groups. Protease treatment of the extract revealed two distinct bands separable on cellulose acetate electrophoresis. The slower moving component was a sulfated glycoprotein while the faster moving component was a sulfated mucopolysaccharide essentially free of protein. This is the first report of specific chemical analyses and electrophoretic separation of a sulfated polysaccharide within the matrix of a member of the Volvocales. The cytochemistry and electrophoretic patterns of theP. caudatapreparation are compared with the same type of extract made fromChlamydomonas reinhardtiiDang. The possible evolutionary significance of the electrophoretic patterns is presented.