Characterization of fimbriae from Bacteroides fragilis

Fimbriae derived from Bacteroides fragilis strain BE1 (BE1 fimbriae) appeared to be composed of subunits with a molecular weight of 40,000. Under the electron microscope the fimbriae could be visualized as straight filaments with a diameter of 4 nm. It appeared that production of the BE1 fimbriae is repressed under conditions of iron limitation, and at a growth temperature of 20 degrees C. Antibodies raised against the 40,000 dalton polypeptide, purified by means of preparative SDS-polyacrylamide gelelectrophoresis, recognized the native fimbriae, as was shown by immunogold labelling of intact bacterial cells, and by immunoprecipitation. Immunoblot experiments showed that other strains of B fragilis tested produced polypeptides, ranging in molecular weight from 40,000 to 42,000, that are antigenically related to the BE1 fimbrial subunit. No haemagglutination activity could be associated with the BE1 fimbriae.