Streptococcus sanguis demonstrated a high affinity for hydrocarbon solvents. When aqueous suspensions of the organism were mixed with either hexadecane or toluene, the cells tended to bind to the nonaqueous solvent. Increases in temperature resulted in a greater affinity of cells for hexadecane. Interaction between the cells and hexadecane was also enhanced by dilute aqueous sodium chloride and by low pH (pH < 5). The results suggest that the cell surface of S. sanguis has hydrophobic properties. Isolated cell walls also tended to partition into the nonaqueous solvent. Amino acid analyses of the walls revealed the presence of several amino acids which possess hydrophobic side chains. It is likely that the hydrophobic amino acids associated with the cell wall contribute to the hydrophobicity of intact S. sanguis. When the adherence of S. sanguis to saliva-coated hydroxylapatite was measured, it was found that hydrophobic bond-

The adherence of Streptococcus sanguis to hydroxylapatite beads has been analyzed by binding isotherms, Langmuir isotherms, and Scatchard plots. For saliva-coated beads, the Scatchard curves contained components with both positive and negative slopes. The results are interpreted as evidence for positive cooperativity in the binding process. Although all Scatchard curves were similar in shape, distinct differences were observed between saliva samples from different individuals. Salivary agglutinins against whole S. sanguis cells did not appear to influence the shapes of the curves or the extent of adherence. In addition, different strains of S. sanguis yielded similar Scatchard plots. When the binding of S. sanguis to buffer-coated hydroxylapatite beads was analyzed by Scatchard plots or binding isotherms, curves were generated which suggested that either direct ligand-ligand or nonspecific interactions were occurring. Hill plots of the adherence data yielded curves with slopes greater than unity for saliva-coated beads, providing additional support for the view that the interactions between S. sanguis and the pellicle involve cooperative phenomena. In contrast, a Hill plot for the binding data of S. sanguis to buffer-coated hydroxylapatite beads gave a curve with a slope of 0.91 ± 0.07, suggesting negative cooperativity or limited specificity. When adherence data were plotted by the Langmuir method, curves were obtained which could not discriminate between the binding of the bacteria to the hydroxylapatite beads coated with either saliva or buffer. It was also observed that several different proteins and whole saliva tended to inhibit adherence. Scatchard plots, however, describing the binding of S. sanguis to the proteincoated beads were unique and revealed possible specific and nonspecific interactions. Scatchard analyses of binding data may be useful in understanding the mechanism(s) of adherence of streptococci to smooth surfaces.Streptococcus sanguis can be observed in early dental plaque and comprises a significant portion of the oral microbiota found on the tooth surface (3,13,15). The mechanism(s) involved in the attachment of S. sanguis to the salivary pellicle which coats the tooth surface remains obscure. Little is known about the structural requirements of pellicle protein receptors for the bacterial ligands. In fact, several groups report that oral streptococci, including Streptococcus mutans as well as S. sanguis, can bind to hydroxylapatite in the absence of any pellicleforming salivary proteins (4,18).In addition to the difficulties in purifying and characterizing specific bacterial surface components and salivary proteins which interact to form stable complexes, there have been only a few efforts to describe the quantitative relationships in adherence phenomena. Clark et al. (4), Gibbons et al. (10), and Appelbaum et al. (1)have employed the Lapgmuir adsorption isotherm to characterize the quantitative aspects of the adherence of oral streptococci to smooth surfaces. Similarly, Wheeler et al. (27...

Nine strains of oral Fusobacterium were examined for their ability to coaggregate in vitro with four strains of the oral yeast. Candida albicans. All of the Fusobacterium nucleatum strains and Fusobacterium periodontium and Fusobacterium sulci coaggregated to various degrees with all of the Candida strains. Fusobacterium alocis, Fusobacterium mortiferum and Fusobactrium simiae strains did not coaggregate with any of the Candida strains. Exposure of the coaggregating Fusobacterium strains but not the Candida strains to heat, trypsin, and proteinase K eliminated coaggregation. Amphotericin B or trichodermin treatment of the yeast species had no effect. The reactions were inhibited by addition of 0.1 M mannose, glucosamine and alpha-methyl mannoside. All coaggregating pairs were disaggregated by the addition of sodium dodecyl sulfate, but nonionic detergents had no effect. The addition of 2.0 M urea completely reversed coaggregation. Candida strains were sensitive to periodate oxidation, whereas the Fusobacterium strains were stable to this treatment. All coaggregations occurred in the presence of saliva and appeared stronger than in buffer. These data suggest that the coaggregations involve either a protein or glycoprotein on the Fusobacterium surface, which may interact with carbohydrates or carbohydrate-containing molecules on the surface of the Candida. These observations expand the known range of intergeneric coaggregations occurring between human oral microbes and indicate that coaggregation of C. albicans and Fusobacterium species may be an important factor in oral colonization by this yeast. The authors believe this to be the first description of coaggregation concerning a carbohydrate component on the yeast cell and a protein component on the oral bacterial cell.

Eight strains of Actinomyces were examined for their ability to coaggregate in vitro with four strains of Candida albicans. The Actinomyces coaggregated to various degrees with all of the Candida strains. Exposure of the Candida but not the Actinomyces to heat, trypsin, proteinase K, amphotericin B or trichodermin abolished coaggregation. All sugars tested did not inhibit any of the reactions. All coaggregating pairs were disaggregated by the addition of SDS, but nonionic detergents had no effect. The addition of urea or EDTA completely reversed coaggregation. Actinomyces strains were sensitive to periodate oxidation, whereas the Candida strains were unaffected. These data suggest that the coaggregations involve a protein on the Candida surface that may interact with carbohydrates or carbohydrate-containing molecules on the surface of the Actinomyces. These observations expand the known range of intergeneric coaggregations occurring between human oral microbes and indicate that coaggregation of C. albicans and Actinomyces may be an important factor in oral colonization by this yeast.

Actinomyces viscosus T14V-Jl and its fimbria-deficient mutant strain possessing type 1 fimbriae strongly aggregated with latex beads treated with acidic proline-rich protein 1, basic proline-rich proteins, and proline-rich glycoprotein and its deglycosylated derivative. These type 1+ strains did not aggregate with latex beads treated with other proteins, such as salivary amylase, salivary histidine-rich polypeptides, laminin, type 1 collagen, fibronectin, or Clq. The type 1+ strains also adsorbed well to experimental pellicles formed with acidic proline-rich protein 1, basic proline-rich proteins, and proline-rich glycoprotein and its deglycosylated derivative on hydroxyapatite (HA) surfaces. These interactions were inhibited with immunoglobulins and Fabs specific for type 1 fimbriae. Type 1-actinomyces exhibited feeble adsorption to latex beads or HA treated with any of the aforementioned proteins. Collectively, these data indicate that actinomyces type 1 fimbriae may specifically interact with several proline-rich salivary molecules, forming experimental pellicles on HA or polystyrene surfaces. PRPs (bPRPs) were localized in the included fractions from the Sephadex G-200 after samples were monitored by amino acid analysis (22). Acidic PRP-1 isolated as previously described (15) was kindly provided by D. I. Hay (Forsyth Dental Center, Boston, Mass.). Commercial human salivary amylase (Sigma Chemical Co., St. Louis, Mo.) was purified further by gel filtration on columns (1.5 by 110 cm) of Bio-Gel P60 (