[Structure and constituents of Brucella. Characterization and biological properties of the fractions]

Abstract

The analysis of the components of a bacterium may be envisaged from the biological aspect (fractionation), the ultrastructural aspect (staining of the structures examined electron-microscopically), and the biological aspect (measure of an activity). In this report we attempt to examine the components of brucella from all three aspects simultaneously. The brucella envelopes have the same ultrastructure as that of gramnegative bacteria: outer membrane, thick stratum or peptidoglycane, periplasmic space, cytoplasmic membrane. The outer membrane of brucella in phase S contains many types of polysaccharides: (1) the lipopolysaccharide (LPS) (S) and polysaccharide B are solubilized by the phenol-uater and ether-water methods, by trichloracetic acid (TCA), by heated sodium dodecyl-sulfate (SDS). The exact localization of polysaccharide B is not known; by the phenol-water extraction method, the LPS (S) in its toxic form (endotoxin) passes in solution into the phenol phase, unlike the endotoxin of enterobacteria, which passes into the aqueous phase. In addition to its toxicity, this LPS (S) is responsible for reactions of immediate hypersensitivity as well as serological reactions towards the standard antigen. It presents A + M antigenic sites; (2) one or more of the polysaccharides remains unsolubilized by the ether-water method, but solubilized by heated SDS; (3) a polysaccharide is linked to peptidoglycane. The structure of the outer membrane of the brucella in phase R is analogous to that of LPS, carrying antigen R, characteristic of these strains. This antigen may be utilized for the serological diagnosis of infections due to brucella R (B. ovis) or vaccinations by a vaccine in phase R. The peptidoglycane fraction extracted by the heated SDS has a more complex structure than that of E. coli: it consists of a supplementary outer layer containing amino acids and polysaccharides. This fraction has a vaccinal activity. A soluble protein fraction, without organized structure, no doubt of cytoplasmic origin, may be extracted by a cold saline solution. This fraction, known as "brucelline", reveals delayed hypersensitivity when injected intradermally. The biological activity of the other structures (periplasm, cytoplasmic membrane, ribosomes...) is not known. Biological activities have been attributed to fractions, but since these are badly defined from the structural point of view it is difficult to determine the connection between activities and structures.