Coaggregation between Actinomyces viscosus T14V and Streptococcus sanguis 34 depends on interaction of a lectin on A. viscosus T14V with a cell surface carbohydrate on S. sanguis 34. This carbohydrate was isolated, and its chemical makeup was established. The carbohydrate remained attached to S. sanguis 34 cells through extraction with Triton X-100 and treatment with pronase. It was cleaved from the cell residue by autoclaving and purified by differential centrifugation and column chromatography on DEAE-Sephacel and Sephadex G-75. The polysaccharide contained phosphate which was neither inorganic nor monoester. Treatment with NaOH-NaBH4, followed by Escherichia coli alkaline phosphatase, or with 48% HF at 4°C, followed by NaBH4, yielded inorganic phosphate and oligosaccharide alditols. Therefore, the polysaccharide is composed of oligosaccharide units joined together by phosphodiester bridges. The structure and stereochemistry of the main oligosaccharide alditol was established previously ( nuclear magnetic resonance studies on the whole polysaccharide revealed the position of the phosphodiester linkages. The polysaccharide is mainly a polymer of (6) GalNAc(al-3)Rha(frl-4)Glc(I1-6)GalftIl-6)GalNAc(P1-3)Gal(a1)-OPO3. It reacted as a single antigen with antiserum to S. sanguis 34 cells and was a potent inhibitor of coaggregation between A. viscosus T14V and S. sanguis 34. Quantitative inhibition of precipitation assays with oligosaccharides, O-allyl N-acetylgalactosaminides, and simple sugars indicated that specific antibodies were directed to the GalNAc end of the hexasaccharide unit. In contrast, coaggregation was inhibited much more effectively by saccharides containing OiGalNAc. Thus, the specificity of the A. viscosus T14V lectin is strikingly different from that of antibodies directed against the S. sanguis 34 polysaccharide.Many of the specific adherence interactions between different bacterial species in dental plaque (15) appear to involve cell-associated lectins on one organism interacting with carbohydrates on another (7-9, 12, 17, 22, 23). One such interaction, lactose-sensitive coaggregation of Actinomyces viscosus T14V with Streptococcus sanguis 34, involves a lectin on A. viscosus T14V and a carbohydrate on S. sanguis 34. Studies have shown that this coaggregation is inhibited much more effectively by Gal,-OMe than by Gala-OMe and more so by Gal(,B1-3)GalNAc than by any other of several disaccharides tested (24-26). While such findings contribute to characterization of the A. viscosus T14V lectin, they provide little insight as to the structure(s) of lectin receptors on S. sanguis 34. We now describe the isolation and characterization of a coaggregation-inhibitory polysaccharide (CIP) from S. sanguis 34 cells that inhibits coaggregation of this organism with A. viscosus T14V and which presumably functions as the receptor on the streptococcal surface.

Coaggregation between Actinomyces viscosus T14V (T14V) and Streptococcus sanguis 34 (Ss34) depends upon specific reaction between lectin on T14V and carbohydrate on Ss34. Studies on coaggregation inhibition by sugars related to Dgalactose, ,B-galactosides, and amphipathic molecules revealed: (i) D-fucose, Dtalose approximately equal to D-galactose, which was 0.2 potency of lactose. No other hexoses or pentoses inhibited at 0.1 M. (ii) GalP(1->3)GalNAcaOCH2C6H5 was the most potent P-galactoside inhibitor; it had 20 times the potency of lactose.

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Specificities of lectins on Actinomyces viscosus T14V and Actinomyces naeslundii WVU45 were compared by measuring the abilities of D-galactose, N-acetyl-D-galactosamine, 14 P-D-galacto-oligosaccharides, and 2 ,-D-fuco-oligosaccharides to inhibit coaggregation between Streptococcus sanguis 34 and each actinomycete. Inhibition profiles were similar, but WVU45 was significantly more sensitive to several inhibitors. D-Galactose-p(1-) 3)-N-acetyl-D-galactosamine

The location of T4D phage-induced dihydrofolate reductase (dfr) has been determined in intact and incomplete phage particles. It has been found that phage mutants inducing a temperature-sensitive dfr (dfr-s) produce heat-labile phage particles. The structural dfr produced by these ts mutants was shown to assume different configurations depending on the temperature at which the phage is assembled. Morphogenesis of incomplete phage particles lacking the gene 11 protein on their baseplates was found to be inhibited by reagents binding to dfr, such as antibodies to dfr. Further, cofactor molecules for dfi, such as