Chemical Composition and Structure of the Cell Wall of Halococcus morrhuae

The chemical composition of trypsin-treated cell walls of three strains of Halococcus morrhuae was determined. Neutral sugars (glucose, mannose, galactose), uronic acids (glucuronic and galacturonic acids), amino sugars (glucosamine, galactosamine), gulosaminuronic acid, acetate, glycine and sulfate were found as major constituents. The cell wall of H. morrhuae CCM 859 was studied in more detail. The major cell wall polymer of this strain is a complex heteroglycan which seems to be responsible for the rigidity and stability of the cell wall. The amino groups of the amino sugars are predominantly N-acetylated. A substitution of the amino groups with glycine instead of acetate could be found for part of the glucosamine residues. Sulfate groups are covalently bound as esters to secondary hydroxyl groups in equatorial conformation. Based on periodate cleavage and permethylation studies of the cell wall and analyses of isolated oligosaccharides, the chemical structure of the cell wall polymer can be proposed as follows:

Sulfate groups are linked to hydroxyl groups in positions 2 and/or 3 of uronic acids, galactose and galactosamine residues. Glucose, galactose, galacturonic acid and all amino sugars are 1 → 4 glycosidically linked in the cell wall polymer. A part of the glucose, galactose and to a lesser extent mannose residues possess more than two glycosidic linkages and represent possible branching points. Glycine residues may play a role in connecting glycan strands through peptidic linkages between the amino group of glucosamine and the carboxyl group of an uronic acid or gulosaminuronic acid.