Escherichia coli L-19 isolated from a healthy individual did not agglutinate with any of 21 polyvalent antisera that cover 174 E. coli O-serogroups. The strain was studied in respect to the O-antigen (O-specific polysaccharide, OPS) structure and genetics. The LPS was isolated by phenol-water extraction of bacterial cells and cleaved by mild acid hydrolysis to yield the OPS. The OPS was studied by sugar and methylation analyses, along with 1D and 2D 1 H and 13 C NMR spectroscopy. The established structure of the linear tetrasaccharide repeating unit was found to be unique among known bacterial polysaccharide structures. A peculiar component of the L-19 OPS was an amide of glucuronic acid with 2-amino-1,3-propanediol (2-amino-2-deoxyglycerol) (GroN). The O-antigen gene cluster of L-19 between the conserved genes galF and gnd was sequenced, and gene functions were tentatively assigned by a comparison with sequences in the available databases and found to be in agreement with the OPS structure. Except for putative genes for synthesis and transfer of GroN, the sequences in the L-19 O-antigen gene cluster were little related to those of reference strains of the 174 known E. coli O-serogroups. The data obtained suggest that L-19 can be considered as a candidate for a new E. coli O-serogroup.
The analysis of fatty acid profiles of lipopolysacharid.es has shown that R. solanacearum strains tested may be divided into two groups. The first group is represented by R. solanacearum strains (5712, 7945, 7955 and 8110) the lipids A of which contained hydroxylated fatty acids with long chains: 3-hydroxy tetradecanoic, 2-hydroxyhexadecanoic and 2-hydroxyoctadecanoic. The second group was represented by R. solanacearum strains the lipids A of which contained hydroxylated fatty acids with short chains: 3-hydroxydecanoic, 2-hydroxydodecanoic and 3-hydroxydodecanoic. 3-hydroxytetradecanoic acid was observed in a small amount. A comparative analysis of the fatty acid composition and biological activity gives a possibility to suppose that 3-hydroxytetradecanoic, 2-hydroxyhexadecanoic and 2-hydroxy octadecanoic acids may be responsible for the toxicity and pyrogenicity of the lipopolysaccharides tested.
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