CELL-SURFACE POLYPEPTIDE CSHA MEDIATES BINDING OF STREPTOCOCCUS-GORDONII TO OTHER ORAL BACTERIA AND TO IMMOBILIZED FIBRONECTIN

Isogenic mutants of Streptococcus gordonii DL1 (Challis) in which the genes encoding high-molecular-mass cell surface polypeptides CshA and/ or CshB were inactivated were deficient in binding to four strains of Actinomyces naeslundii and two strains of Streptococcus oralis, Lactos e-sensitive interactions of S. gordonii with A, naeslundii ATCC 12104 and PK606 were associated with expression of cshA but not of cshB. Lac tose-insensitive interactions of S. gordonii with A. naeslundii T14V a nd WVU627, and with S. oralis C104 and 34, were dependent on expressio n of cshA and cshB. S. gordonii DL1 cells bound to immobilized human f ibronectin (Fn), but not to soluble Fn, in a dose-dependent manner, an d binding was noninhibitable by heparin. S. gordonii cshA and cshB mut ants were also deficient in binding to immobilized human Fn. Antibodie s to an NH2-terminal nonrepetitive region (amino acid residues 42 to 8 86) of recombinant CshA inhibited binding of S. gordonii DL1 cells to A. naeslundii T14V and PK606 and to immobilized Fn. Conversely, antibo dies to an amino acid repeat block segment of the COOH-terminal domain (amino acid residues 2026 to 2508) were not inhibitory to adherence. Assays using CshA specific antibodies revealed that surface expression of CshA was reduced in cshB mutants. The results suggest that CshA ac ts as a multifunctional adhesin in S. gordonii and that major adhesion -mediating sequences are specified within the nonrepetitive NH2-termin al region of the polypeptide.