A phosphorylated polysaccharide was isolated from the aqueous layer of the phenol-water extract of a non-halophilic bacterium Shewanella putrefaciens strain $29. The glycosyl phosphate linkage in the polysaccharide was split under mild acid conditions to give, after borohydride reduction, a phosphorylated oligosaccharide-alditol. On the basis of sugar analysis and ¹H, ¹³C and ³¹P NMR spectroscopy, including 2D COSY, relayed COSY, rotating-frame NOE spectroscopy (ROESY), heteronuclear ¹³C,¹H COSY, and H-detected heteronuclear ¹H,³¹P multiple-quantum coherence (HMQC), it was concluded that the polysaccharide is built up of tetrasaccharide-phosphate repeating units having the following structure:4)-α-L-QuipNAc-(1→3)-α-D-GlcpNAc-(1→3)-β-D-Quip4NAc-(1→3)-α-D-Galp-1-P-(Owhere QuiNAc and Qui4NAc are 2-acetamido-2,6-dideoxyglucose and 4-acetamido-4,6-dideoxyglucose, respectively.