Immunochemistry of the cell surfaces of Bacteroides bivius and Bacteroides disiens

Abstract

Outer membranes were extracted from seven strains of Bacteroides bivius and six strains of B. disiens by the Sarkosyl method. Lipopolysaccharides (LPS) were extracted from the same strains by the Proteinase K method, and from three strains of each species by an aqueous phenol method. Analysis of the outer-membrane proteins by SDS-PAGE demonstrated that, within a species, very similar patterns with many shared or common bands were produced, but there were sufficient differences between species to allow separation. Immunoblotting with antisera raised against whole cells of each of the type strains showed that many antigens were shared between species. Smooth LPS was present in both species. By immunoblotting, the O-antigen of B. disiens was shown to be common to all six strains, and there was no cross-reaction between the B. disiens antiserum and B. bivius LPS. The O-antigen of B. bivius was not detected by immunoblotting with homologous antiserum, but antiserum to B. bivius reacted with a series of common low molecular mass antigens that were present in LPS preparations from strains of both species.