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.