Streptococcal binding to salivary mucin MUC7. Untreated (Ø) or sialidase-treated (S) whole saliva (WS) as well as parotid (PAR), and submandibular/sublingual glandular secretions (SMSL) were separated by SDS-PAGE under reducing conditions, transferred to nitrocellulose and overlaid with fluorochrome-labeled bacteria. A, Periodic acid-Schiff stain to reveal the glycosylated mucin bands. B, Immunoblot with anti-MUC7 antibody. C, Bacterial overlay with fluorochrome-labeled S. gordonii DL1, S. sanguinis SK36, encapsulated S. pneumoniae wild-type strain TIGR4, capsule-free mutant strain HR1001.1, and respective isogenic SRR adhesin-deficient mutants. Fluorescent signals of bound antibodies or bound bacteria were detected using a fluorescence scanner.