Structural and Genetic Relationship of the O-Antigens of the Type Strains Azospirillum agricola CC-HIH038 and Azospirillum doebereinerae GSF71

A lipopolysaccharide was isolated from cells of the type strain of a rhizobacterium Azospirillum agricola CC-HIH038 by phenol extraction. The O-specific polysaccharide was obtained by mild acid hydrolysis of the lipopolysaccharide followed by chromatographic fractionation. Monosaccharide analysis, including determination of absolute configurations and 1D and 2D 1H and 13C NMR spectroscopy, revealed the following structure of the O-specific polysaccharide repeating unit of A. agricola CC-HIH038T: →3)-α-L-Rhap2Ac-(1 → 3)-α-L-Rhap-(1 → 3)-α-L-Rhap-(1 → 3)-β-D-GlcpNAc6Ac-(1→. This unit is structurally related to that of A. doebereinerae GSF71T. Based on the analysis of full-genome sequencing data for strains A. agricola CC-HIH038T and A. doebereinerae GSF71T, the loci for O-specific polysaccharide biosynthesis have been identified. They were characterized by similar organization and a high level of gene homology, confirming the common structure of the O-antigens of these strains.