Rapid biological and chemical analyses of bacterial endotoxins separated by preparative thin-layer chromatography

Column liquid chromatography of endotoxins

A new, fast and highly reproducible column liquid chromatographic method was elaborated for the analysis and small-scale preparative isolation of endotoxin from Serratia marcescens Bizio (ATCC No. 264). This procedure detects contaminants of such preparations with high sensitivity and it is capable of separating them from endotoxic components. Extensive heterogeneity of both 5% trichloroacetic acid and phenol-water-extracted endotoxin preparations was recorded. Heterogeneity among the endotoxic components of purified preparations could also be detected by this method. Measurements of biological activities, such as Limulus amoebocyte lysate activation, lymphoblastogenesis (mitogenicity) and tumor necrosis factor (TNF) liberation were carried out on the chromatographically separated fractions. During these studies, non-toxic but in vitro TNF-generating components of crude endotoxin extracts were also detected.

Thin-layer chromatography of endotoxins, their derivatives and contaminants

Thin-layer chromatographic (TLC) separation techniques were used to analyze the heterogeneity of various preparations which included smooth and rough endotoxins (ET), Lipid A precipitates and synthetic Lipid A samples and a novel cytotoxic bacterial lipid. Furthermore, carbohydrate-rich split products (PS) of ET were also separated on commercial silica-coated plates. Satisfactory results were obtained by two-dimensional TLC or by the combination of chromatography followed by high-voltage electrophoresis in the separation of PS of ET cleaved by mild acetic hydrolysis. Several spray reagents were found which were eminently suitable to detect carbohydrate containing compounds. Less specific but generally useful spray reagents were also developed which gave strong color reactions with lipids, proteinaceous and carbohydrate containing split products of the ET preparations. Improved chromatographic resolution has also revealed substantial heterogeneity in both rough and smooth ET samples. Three biological activities of the separated components could be determined. These were antigenicity detected by reactivity with monoclonal antibodies on the TLC plates, endotoxicity, determined by the Limulus amoebocyte lysate (LAL) test and direct cytotoxicity of P815 cells in vitro. Considerable amounts of non-endotoxic and non-antigenic contaminants could be detected in all preparations tested. Significant amounts of free Lipid A were also found in smooth ETs. Thus a new level of complexity is recognized by TLC within these preparations.

Cytotoxicity of a novel lipid-like bacterial product

A highly cytotoxic, lipid-like compound was isolated from a Serratia marcescens strain currently under identification. We have named the compound DCX for its direct cytotoxic activity on various cell types in culture. DCX was purified by preparative thin layer chromatography from chloroform: methanol = 4:1 extracts of whole bacteria, and is chromatographically homogeneous. The effect of DCX on cells is dose, time, and temperature dependent. DCX is particularly toxic to the mastocytoma cell line P815 (TD50 = 75 pg/ml). Three other malignant or transformed murine cell lines were sensitive to the cytotoxic action of DCX. The effect of DCX was also tested on normal cells (human gingival fibroblasts), which showed greater resistance to DCX than the other cells tested.

Biological activities of lipopolysaccharide fractionated by preparative acrylamide gel electrophoresis

Lipopolysaccharide from a smooth strain of Salmonella minnesota was fractionated into two major fractions and one intermediate fraction by using sodium dodecylsulfate-polyacrylamide gel electrophoresis. On the basis of the study by Hitchcock and Brown, it was deduced that the top fraction was mainly long O-side chain LPS and the bottom fraction was O-side chain-less LPS. The middle fraction was a mixture of both short O-side chain LPS and O-side chain-less LPS. The antigenic properties and biological activities were not altered in this fractionation procedure. Comparison of the biological activities of the top fraction with those of the bottom fraction revealed that the bottom fraction had higher activity in polyclonal B-cell activation and spleen-swelling effect and that there was no significant difference in adjuvant activity, ability to render macrophages cytotoxic, induction of colony-stimulating factor and the ability to induce the Schwartzmann reaction. It was suggested that O-side chain makes no contribution to the latter biological activities including adjuvant activity of S. minnesota LPS.

Relationship of structure to function in bacterial endotoxins. IX. Differences in the lipid moiety of endotoxic glycolipids

Chemical, immunochemical, chromatographic, and endotoxic properties of five chromatographically pure glycolipids were compared. The preparations were extracted by chloroform-methanol from three Escherichia coli, one Salmonella minnesota, and one S. typhimurium Re heptoseless mutant strains. The local Shwartzman skin assay, the nonspecific resistance-enhancing effect, and the Limulus assays could not distinguish among the five glycolipids, all five being active in all three assays. Significant differences could be seen when the tumor resistance-enhancing effect of the glycolipids in mice was compared with the nonspecific TA3-Ha murine mammary adenocarcinoma growing in ascites form. Even greater variation was observed in the capacity of the preparations to enhance the nonspecific resistance of mice to virulent S. typhi 0901 infections. The data show that the five glycolipids are quite dissimilar in their biological effects. Similarly, thin-layer chromatography and molecular ratio determinations showed that differences exist in the chemical structure of the glycolipids. Accordingly, we claim that not only the polysaccharide but the lipid moiety as well may vary in various gram-negative endotoxin preparations.