Abstract
Strains representing taxonomic clusters of Actinomyces viscosus and Actinomyces naeslundii were studied by indirect immunogold electron microscopy with either monospecific anti-type 1 and anti-type 2 rabbit antibodies or species-specific monoclonal antibodies. The monoclonal and anti-type 2 antibodies localized on long fibrils, whereas the anti-type 1 antibodies mostly localized close to the cell body or on shorter appendages.