CAPSULAR POLYSACCHARIDES OF SERRATIA MARCESCENS

Abstract

Four polysaccharides were isolated from the capsular layer of Serratia marcescens cells grown on a sucrose medium. In composition, electrophoretic behavior, and sedimentation in the ultracentrifuge, all were shown to be markedly different. Analytical data indicated that the polysaccharides were an acidic glucomannan (I), a rhamnoglucan (II), a glucoheptan (III), and a rhamnoheptoglucan (IV). In I, in addition to the main acidic component D-glucuronic acid, a small amount of guluronic acid was also identified. A relatively high protein or peptide content in the purified polysaccharides suggested that it was firmly bound to the carbohydrate structure; "bound" lipid consisting mainly of hydroxymyristic acid was also a part of the structure. Methylation studies established the main glycosidic linkages in I, II, and III. The capsular polysaccharides had properties similar to those of polysaccharides isolated from a culture filtrate of S. marcescens in an earlier study, and a possible relationship between these two groups of polysaccharides is discussed.