Structural Elucidation of the Nonclassical Secondary Cell Wall Polysaccharide from Bacillus cereus ATCC 10987 COMPARISON WITH THE POLYSACCHARIDES FROM BACILLUS ANTHRACIS AND B. CEREUS TYPE STRAIN ATCC 14579 REVEALS BOTH UNIQUE AND COMMON STRUCTURAL FEATURES

Nonclassical secondary cell wall polysaccharides constitute a major cell wall structure in the Bacillus cereus group of bacteria. The structure of the secondary cell wall polysaccharide from Bacillus cereus ATCC 10987, a strain that is closely related to Bacillus anthracis, was determined. This polysaccharide was released from the cell wall with aqueous hydrogen fluoride (HF) and purified by gel filtration chromatography. The purified polysaccharide, HF-PS, was characterized by glycosyl composition and linkage analyses, mass spectrometry, and one-and two-dimensional NMR analysis. The results showed that the B. cereus ATCC 10987 HF-PS has a repeating oligosaccharide consisting of a -> 6)-alpha-GalNAc-(1 -> 4)-beta-ManNAc-(1 -> 4)-beta-GlcNAc-(1 -> trisaccharide that is substituted with beta-Gal at O3 of the alpha-GalNAc residue and nonstoichiometrically acetylated at O3 of the N-acetylmannosamine (ManNAc) residue. Comparison of this structure with that of the B. anthracis HF-PS and with structural data obtained for the HF-PS from B. cereus type strain ATCC 14579 revealed that each HF-PS had the same general structural theme consisting of three HexNAc and one Hex residues. A common structural feature in the HF-PSs from B. cereus ATCC 10987 and B. anthracis was the presence of a repeating unit consisting of a HexNAc(3) trisaccharide backbone in which two of the three HexNAc residues are GlcNAc and ManNAc and the third can be either GlcNAc or GalNAc. The implications of these results with regard to the possible functions of the HF-PSs are discussed.