Distribution of capsular materials on the cell wall surface of strain Smith diffuse of Staphylococcus aureus.

The fine structure of the capsule of Staphylococcus aureus Smith diffuse was examined by the technique of freeze-substitution and immunoelectron microscopy. The cell surface was covered with a thick layer consisting of fine fibrous structures which were absent from an unencapsulated strain, Smith compact. Anti-teichoic acid antibody did not react with this surface layer but reacted with the surface of strain Smith compact. Anti-capsular antibody, made from the serum of a rabbit immunized with strain Smith diffuse and specific absorption with unencapsulated strain Wood 46, reacted with the fibrous layer of the Smith diffuse strain. Since the anti-teichoic acid antibody did not react with the encapsulated strain Smith diffuse, the capsular layer acts as a barrier to penetration of the anti-teichoic acid antibody through the capsular layer. A portion of a few cell surfaces of the encapsulated strain remained accessible to the anti-teichoic acid antibody. The capsular layer in this portion of the cell surface was thin, and this surface seemed to be a new cell wall surface created by the cell separation.