Relation of structure to function in bacterial O antigens. II. Fractionation of lipids present in Boivin-type endotoxin of Serratia marcescens.

Nowotny, Alois (City of Hope Medical Center, Duarte, Calif.). Relation of structure to function in bacterial O antigens. II. Fractionation of lipids present in Boivin-type endotoxin of Serratia marcescens. J. Bacteriol. 85:427-435, 1963.-Methods for liberation of lipids from their endotoxic O antigen were investigated. In the case of endotoxin isolated from a chromogenic Serratia marcescens, best results were obtained with diluted formic acid. The crude lipid mixture consisted of at least 16 different components, which were analyzed by paper chromatography. Good separation was achieved by silicic acid-impregnated paper. Lipids were stained with metachromatic o-toluidine blue. Solubility of the crude lipid mixture was studied in different organic solvents. Preparative fractionation was developed utilizing various organic solvents on the basis of solubility differences of the lipid components. Pure fractions were obtained by silicic acid column chromatography. Since none of the lipid liberation methods so far developed can produce undegraded lipids free from split products and remnants of cell-wall polysaccharides, their usefulness is limited in comparing the chemical structure of the liberated lipid with that of the lipid intact in the cell wall. The liberation procedures cause changes within the lipid structure itself, which in turn would alter whatever potential ability it might have to elicit certain biological reactions.