Exopolysaccharide and storage polymer production in Enterobacter aerogenes type 8 strains

Many exopolysaccharide (EPS)-producing bacterial strains also synthesize storage polymers. The production of slime EPS and of the storage polymer glycogen was compared in batch cultures of EPS⁺ and EPS^- isogenic strains of Enterobacter aerogenes type 8. Conditions of nutrient imbalance with high C: N ratios favoured both EPS and storage polymer synthesis and resulted in little subsequent degradation of glycogen. In the EPS⁺ strain, glycogen synthesis was consistently lower than in the EPS^- strain, indicating that substrate was preferentially used for EPS production. Reduced levels of carbon substrate in the growth medium resulted in lower storage polymer synthesis and in the degradation of the glycogen formed in EPS-producing bacteria. Considerable differences in the synthesis and breakdown of intracellular carbohydrate were observed between bacteria grown in synthetic media with ammonium salts and the same bacteria grown in medium with casein hydrolysate as the nitrogen source. Growth in media depleted in magnesium was slower than in complete media but high yields of glycogen were obtained in both the EPS⁺ and EPS^- strains.