Outer membrane proteins of thebacteroides fragilis group

The Triton-insoluble outer membrane proteins of members of the obligately anaerobicBacteroides fragilis group were examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The application of previously published methods for the preparation of outer membranes from these anaerobes led to relatively low recoveries of outer membrane material. Additionally, the outer membrane recovered was not qualitatively or quantitatively representative of the total outer membrane. A method previously devised for the isolation of the outer membrane proteins fromEscherichia coli was used. By this method, the members of theB. fragilis group were found to possess a striking capacity to alter their cell-surface proteins in response to cultivation in different media.