Some Observations on the Synthesis of Polysaccharides by Soil Bacteria

Abstract

A Bacillus subtilis variety isolated from the soil differed from other strains of this organism and related forms, in that a fructosan was synthesized from sucrose when inorganic as well as organic N was used as the N source. This organism when first isolated also synthesized a polysaccharide from several common sugars other than sucrose, but soon lost its ability to do so. There was evidence that the latter material was different in nature from the fructosan produced from sucrose. Azotobacter indicum was found to synthesize chiefly a fructosan from sucrose. The physical properties of this material were different from the fructosan synthesized by B. subtilis and related species. When cultured on glucose agar, A. indicum synthesized a dextran containing over 30% glucuronic acid units. Two unidentified organisms, a Gram-negative rod, and a Gram-positive rod synthesized dextrans containing uronic acid units when grown on sucrose medium. Slimy capsular material was produced from a wide variety of carbohydrates including plant extracts. In general, the bacterial polysaccharides were much less readily utilized as carbon and energy sources by bacteria, actinomycetes, and fungi than was glucose. The dextran produced by the Gram-negative rod was most resistant to decomposition. Only 3 Actinomycetes were apparently able to utilize it. The Gram-positive rod and B. subtilis were able to utilize the polysaccharides they synthesized.