Factors influencing the polysaccharide content of Escherichia coli

Abstract

The polysaccharide content of E. coli. grown under various conditions, was detd. by acid hydrolysis of washed cell suspensions, followed by detn. of reducing sugars by the method of Somogyi. The polysaccharide content falls during the stationary phase, but the onset of this fall does not exactly coincide with the cessation of cell division. In a glucose-ammonium salt medium this trend is obtained whether exhaustion of N or exhaustion of glucose determines the onset of the stationary phase. For these reasons the fall is not attributed to the utilization of stored polysaccharide by the cells when the sugar in the medium is used up. For lactose, galactose and glucose, grown at pH 7.5 in an amino acid medium which will support some growth in the absence of a sugar, the stored polysaccharide increases markedly with sugar concn. to a max., beyond which further additions cause no increase. With mannose and fructose little increase is produced. At a fixed sugar concn., variation of pH affected the storage of cells grown in glucose and galactose media. In these cases there are pH optima, which are not shown with the low-storing sugars, mannose and fructose. There is a wide variation of stored polysaccharide content for different strains of E. coli grown under identical conditions. The Sahyun method of glycogen detn., coupled with the Hagedorn and Jensen method for reducing sugars, is not satisfactory for the estimation of total bacterial polysaccharide. The increased storage of polysaccharide, reported when this method of estimation was used and the cells were grown in the presence of D-phenylalanine, is not confirmed when the method described above is employed.