Structure of teichoic-acid--glycopeptide complexes from cell walls of Bacillus cereus AHU 1030.

Abstract

From lysozyme digests of N-acetylated cell walls of Bacillus cereus AHU 1030, two acidic polymer fractions with molecular weights of about 24000 and 45000 were isolated by ion-exchange chromatography and gel chromatography. These polymer fractions, containing glycerol, phosphorus and glucose in a molar ratio of 1.00:1.00:0.85 together with small amounts of glycopeptide components and mannosamine, were characterized as teichoic-acid-glycopeptide complexes with one and two teichoic acid chains made of 60-65 repeating glycerol phosphate units that were mostly glucosylated. Mild alkali treatment of the complexes yielded a disaccharide-linked glycopeptide. The disaccharide was liberated from the glycopeptide by mild acid treatment and identified as N-acetylmannosaminyl(beta 1 leads to 4)N-acetylglucosamine. On the other hand, the same disaccharide linked to the teichoic acid chain was obtained by direct heating of the cell walls at pH 2.5. These results lead to a conclusion that in the cell walls of this strain the glycerol teichoic acid chain is attached to the glycan chain of peptidoglycan through this disaccharide unit. The disaccharide is linked at its reducing and nonreducing ends to the glycan chain and the teichoic acid chain, respectively, through phosphodiester bridges.