STRUCTURAL FEATURES OF TWO EXTRACELLULAR POLYSACCHARIDES FROM SERRATIA MARCESCENS

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Abstract
A polysaccharide insoluble in acidified ethanol solution has been isolated from a culture filtrate of Serratia marcescens. Fractionation by cetyltrimethylammonium bromide ("Cetavlon") and by diethylaminoethyl (DEAE) cellulose yielded a polysaccharide which was electrophoretically homogeneous and contained D-glucose, L-rhamnose, D-galactose, L-glycero-D-mano-heptose, D-glycero-D-manno-heptose, glucosamine, and galactosamine in an approximate molar ratio of 6.5:3.5:0.5:1.0:0.5:1.0:0.2. However, following methylation it was found that the fully methylated polysaccharide could be fractionated by organic solvents into a rhamnoglucan and a heptoglucan. Both polysaccharides contained lipid material consisting mainly of hydroxy myristic acid and hydroxy lauric acid. The main chain of the rhamnoglucan was composed of (1 → 3) linked L-rhamnopyranose units and (1 → 4) linked D-glucose units with the non reducing end groups being D-glucose; some branching occurred through D-glucose units. The heptoglucan was composed mainly of chains of (1 → 4) linked D-glucose units with smaller amounts of (1 → 6) linked D-glucose and (1 → 2) linked D-glycero-D-manno-heptose units; these chains were terminated by D-glucopyranose and L-glycero-D-manno-heptose end groups.