New structural insights into the cell-wall polysaccharide of the diatom Phaeodactylum tricornutum

The cell wall of diatoms is composed of silica and organic matter, including protein, long-chain polyamines and polysaccharides. The main polysaccharide, a sulphated glucuronomannan, has been observed in many diatoms suggesting that it plays an important role in cell-wall biogenesis. We extracted and purified the polysaccharide, prepared oligosaccharide series and analysed the structure of poly- and oligosaccharides using chromatography and NMR spectroscopy methods. Our results show that the backbone of the polysaccharide is predominantly a linear poly-α-(1 → 3) mannan decorated with sulphate ester groups and β-D-glucuronic residues.