The cellular localization of the major surface protein SpaA of Strepto
coccus sobrinus 6715 was examined by immunoelectron microscopy with ra
bbit polyclonal antibodies directed against purified SpaA protein. Imm
unoelectron microscopic analysis of thin sections of S. sobrinus cells
revealed that the SpaA protein is associated with the fibrillar fuzzy
coat of S. sobrinus cells and appears to be distributed over the enti
re surface of S. sobrinus cells.