Interaction of Gram-negative bacteria with cationic proteins: Dependence on the surface characteristics of the bacterial cell

Gram-negative bacteria can enter the bloodstream and interact with serum cationic proteins. The character of interaction will depend on the surface characteristics of bacterial cells, which are determined by bacterial chemotype and density of lipopolysaccharide (LPS) packing in the cell wall. It was shown that the lysozyme treatment resulted in the increase sensitivity to hypotonic shock. Significant differences to this effect were found between Escherichia coli strain D21 and D21f2 under treatment with physiological protein concentration. On the basis of electrokinetic measurements and studies of the interaction of cells with lysozyme, the hypothesis was formed that the cell wall of the E. coli strain D21f2 contains more LPS and has a higher density of their packing than the cell wall of the E. coli D21 cells. The effect of lysozyme and lactoferrin on the viability of E. coli cells of two different strains was examined. Lysozyme was found to more effectively inhibit the growth of the E. coli D21 bacteria, and lactoferrin suppressed mainly the growth of the E. coli D21f2 bacteria. These results indicate that the differences in LPS core structure of bacterial R-chemotype, which determines surface charge and density of LPS packing, plays an essential role in the mechanisms of interaction of the cationic proteins with the cell wall.