Fatty acid composition of the lipopolysaccharides of bacteria in the genera Escherichia, Shigella and Salmonella as a taxonomic trait

The comparative study of the fatty acid composition of bacterial lipopolysaccharides (LPS) in the genera Escherichia, Shigella, Salmonella has been carried out under identical experimental conditions. The LPS of the bacteria under study have been found to contain a number of saturated fatty acids and oxyacids which could not be previously detected in these bacteria in other studies. In all bacterial strains under study LPS include mainly 3-oxytetradecanoic, tetradecanoic and dodecanoic fatty acids. The essential feature of the fatty acid composition of Salmonella is the presence of 2-oxytetradecanoic acid; this acid is absent in Escherichia and Shigella, which can thus be used as a differentiating criterion. The content of other fatty acids in Salmonella is similar to that in Escherichia and Shigella. These data confirm that the genera Escherichia, Shigella and Salmonella are phylogenetically related, the relationship between Escherichia and Shigella being more close.