Structures of lipopolysaccharides of Pantoea agglomerans modulate bacterial protease activity and human erythrocytes osmotic resistance

Background: Previously we showed that lipopolysaccharides (LPS) of gram-negative bacteria are able to increase the activity of Bacillus proteases and to affect the osmotic resistance of human erythrocytes. Howe­ver the relationship between these effects and the structure of LPS components remains poorly understood. Objective: The aim of this work was to estimate the effect of LPS isolated from six different Pantoea agglomerans strains, the structures of lipid A and O-specific polysaccharide of which were established by us earlier, on the activity of Bacillus proteases with fibrinogenolytic and elastase activity, as well as the effect of four of these LPS on the osmotic resistance of human erythrocytes. Methods: Lipopolysaccharides of Pantoeae agglomerans 8488, 7969, P324, 7604, 8674t, P1а strains were isolated by the hot phenol-water extraction method. Fibrinogenolytic and elastase activity of proteases obtained from Bacillus sp. IMV B-7883 culture was measured spectrophotometrically. To estimate erythrocytes osmotic resistance the blood samples from healthy donors were obtained. Results: The results of the study showed the significant difference in biological activity of LPS of different Pantoeae agglomerans strains. Thus only LPS of P. agglomerans 8488 which contain triacyl form of lipid A significantly modulated proteases with fibrinogenolytic and elastolytic activity. The pronounced reduction of erythrocyte hemolysis was observed only with the treatment of erythrocytes with P. agglomerans 7604 LPS, a distinctive feature of which is the presence of penta- and tetraacyl and the absence of hexaacyl forms of lipid A. Conclusion: The identified differences in LPS hemolytic activity and effects on the activity of bacterial proteases are connected with the diverse structure of LPS components, particular, the lipid A acyl chains composition.