COMPARISON OF CHEMICAL COMPOSITION OF A LIPOPOLYSACCHARIDE AND POLYSACCHARIDE FRACTION ISOLATED FROM BRUCELLA MELITENSIS

Westphal's procedure was found the most suitable for the isolation of lipopolysaccharide fractions from Brucella melitensis cells; only the fraction obtained in the aqueous layer (LPS) is studied in this paper. Beside LPS, an extracellular polysaccharide fraction (PS) was extracted from the culture medium of the bacteria, and the chemical composition of both fractions, LPS and PS, has been compared. In both cases, nucleic acid contaminants were eliminated either by alcohol precipitation or by use of cetavlon. These treatments also removed an acidic polysaccharide containing mainly galactosaminuronic acid, which might be Vi antigen. The main difference between LPS and PS is the presence of a small amount of lipid A in LPS (ca. 1%). As in the case of lipid A isolated from LPS of Enterobacteria, Brucella lipid A contains glucosamine and fatty acids, but β‐hydroxymyristic acid could not be detected. The behaviour of LPS and PS fractions on DEAE‐cellulose columns is very similar, and the small differences that could be observed may be explained by solubility changes due to the lipid moiety present in LPS. Both fractions contain 2‐keto‐3‐hydroxy‐octulosonic acid, a mixture of d‐ and l‐glycero‐d‐mannoheptoses, a high amount of glucose, galactose, a 3,6‐dideoxyhexose (colitose or abequose), and a methylated sugar behaving as a methylated derivative of dideoxyhexose. Small amounts of rhamnose in PS and of arabinose in LPS seem to be due to contaminants. Copyright © 1969, Wiley Blackwell. All rights reserved