SDS-PAGE analysis of proteins released in free-soluble form by biofilm and planktonic A. actinomycetemcomitans D7S, its isogenic pal mutant (D7S-p), or D7SS, detected by Silver-staining (panel A), by Coomassie blue-staining (panel B), and by immunoblotting using an antiserum raised against whole cell antigen of A. actinomycetemcomitans serotype a (panel C). Proteins released to PBS through the 20 nm filters of the inserts were collected after 6 h of incubation. Concentrated samples equal to 1.5 ml filtrate were applied in each well for Silver- and Coomassie blue-staining, and equal to 0.75 ml for immunoblotting. Protein bands corresponding to GroEL and PAL are indicated with arrows. The sizes of the proteins (kDa) in the prestained molecular weight marker (M) are indicated.