Structure of an Acidic Polysaccharide elaborated by Aerobacter aerogenes

Abstract

ORGANISMS of the Aerobacter–Klebsiella group have been divided¹ into many serologically distinct types each of which produces its own type-specific polysaccharide. Only a few of the structures of these polysaccharides have been elucidated^2–4 since in general they are of a highly complex nature. Recently we isolated an acidic polysaccharide (4.45 gm.) from the culture medium (38.4 1.) of Aerobacter aerogenes N.C.T.C. 8172 (Klebsiella type 64). The bacteria were grown both in batches and in continuous culture in an apparatus of the type described by Elsworth, Meakin, Pirt and Capell⁵. A peptone–glucose medium was used, the culture was aerated, the pH 5.0 and the temperature, 37°. The acidic polysaccharide was freed from neutral polysaccharide by precipitation with ‘Cetavlon’⁶ and from nucleic acid by the preferential solubility of its cetyl trimethyl ammonium salt in 0.25 M sodium chloride. Isolated as its sodium salt, the acidic polysaccharide had C, 45.31; H, 6.19; N, 0.81; P, 0.11 per cent and its ultra-violet absorption at 260 mµ corresponded to about 1.8 per cent nucleic acid impurity. The polysaccharide contained 28.7 per cent uronic acid (by decarboxylation⁷) and the infra-red spectra of the polysaccharide as the free acid and as the sodium salt confirmed the presence of carboxylic acid groups⁸. The polysaccharide showed [α]¹⁷ _D + 29.4° (conc. 0.272 in M sodium chloride).