The diacetamidodideoxyuronic-acid-containing glycan chain of Bacillus stearothermophilus NRS 2004/3a represents the secondary cell-wall polymer of wild-type B-stearothermophilus strains

The diacetamidodideoxymannuronic-acid-containing glycan of Bacillus stearot hermolohilus NRS 2004/3a with the repeating unit structure [--> 4)-beta-D-M anpA2,3(NAc)(2)-(1 --> 6)-alpha-D-Glcp-(1 --> 4)-beta-D-ManpA2,3(NAc)(2)-(1 --> 3)-alpha-D-GlcpNAc-(1 -->], was examined to identify its linkage to th e bacterial cell wall. In a previous paper it was suggested that this glyca n is covalently linked to the surface layer (S-layer) glycoprotein of that organism. By improved chromatographic techniques (gel permeation over Sepha cryl S-1000 SF; C4 reversed-phase HPLC) the diacetamidodideoxyuronic-acid-c ontaining material was completely separated from the S-layer glycoprotein. This implicates only low, if any, specific affinity between these cell-wall components. To obtain sufficient amounts for the chemical characterization of its linkage region, the identical diacetamidodideoxyuronic-acid-contain ing material was isolated from sonicated cells of that organism by a purifi cation procedure different to that for preparation of S-layers. This method allowed collection of the intact molecule including its linkage region. Fr om the combined results of the chemical characterization and 600 MHz NMR sp ectroscopy it is proposed that the diacetamidodideoxyuronic-acid-containing glycan chain, consisting of approximately six tetrasaccharide repeating un its, is directly linked via a pyrophosphate bridge to carbon 6 of muramic a cid residues of the peptidoglycan sacculus. About 20-25% of the muramic aci d residues are substituted with these polysaccharide chains. Thus, the diac etamidodideoxyuronic-acid-containing glycan represents a secondary cell-wal l polymer of B, stearothermophilus NRS 2004/30.