COMPARATIVE STRUCTURES OF THE CELL-WALL POLYSACCHARIDES OF FOUR SPECIES OF THE GENUS MICROBACTERIUM

Abstract

Cell-wall polysaccharides purified from four species of the genus Microbacterium were characterized in relation to their taxonomy, based on ¹H-NMR and ¹³C-NMR spectrometry, methylation analysis and Smith degradation.
The polysaccharide isolated from M. imperiale IFO 12610 contained a backbone consisting of heptasaccharide repeating-units, to which side chains of L-rhamnopyranosyl-(1→2)-D-mannopyranosyl-(1→2)-D-mannopyranoses as branches were attached to position 6 of the 3-linked D-galactopyranose residues. The polysaccharide of M. lacticum IFO 14135 contained hexasaccharide repeating-units, to which disaccharide groups of L-rhamnopyranosyl-(1→2)-L-rhamnopyranoses were attached to position 6 of the 3-linked D-galactopyranose residues to form branches. The polysaccharide of M. arborescens IFO 3750 consists of pentasaccharide repeating-units, and single D-mannopyranosyl groups were attached as branches to position 6 of the 3-linked D-galactofuranose residues. The polysaccharide of M. laevaniformans IFO 14471 had a more complicated structure consisting of decasaccharide repeating-units, and branches occur at three different positions.
Thus, the cell-wall polysaccharides of the former three species were similar in their basic structures, but that of M. laevaniformans has a significantly different structure. These results indicated that the structures of cell-wall polysaccharides are heterogeneous in the genus Microbacterium and may characterize the species in the genus.