Abstract
Adhesion of oral mitis group streptococci such as Streptococcus gordonii to acquired pellicle of the tooth surface is the initial step of oral biofilm formation. S. gordonii wild type strain DL1 possesses Hsa adhesin, recognizing terminal sialic acid of the host sialoglycoconjugates. The aim of the present study was to investigate the role of Hsa adhesin in biofilm formation. Biofilm-forming ability of the S. gordonii hsa mutant in microtiter plates pre-coated with saliva, fetuin and mucin was significantly reduced, compared to that of DL1. In contrast, no significant difference in biofilm-forming ability was observed in the plates pre-coated with bovine serum albumin, which does not contain sialic acid. Biofilm-forming ability of DL1 in saliva-coated microtiter plate was significantly reduced when the plate was pre-treated with neuraminidase. The sialic acid-dependent biofilm-forming ability varied among different S. gordonii wild type strains. However, Southern blot analysis and Western blot analysis showed all the wild type strains appear to possess and express the hsa homologue, respectively. These results suggest that binding of Hsa adhesin to sialoglycoconjugates is associated with biofilm formation of S. gordonii DL1, and imply variation in the contribution of Hsa and its homologues to S. gordonii biofilm formation.
