Specific coaggregation and the cell wall of Streptococcus sanguis
Journal of Bacteriology
Sacculi prepared from Streptococcus sanguis 34 by extensive extraction of cells with hot sodium dodecyl sulfate-2-mercaptoethanol retained the ability to coaggregate with Actinomyces viscosus T14V. When S. sanguis 34 was disrupted by homogenization with glass beads and fractionated by differential centrifugation, only the cell wall fraction agglutinated A. viscosus T14V. When strain 34 was treated with lysozyme, the coaggregating capability of the cells was essentially unaltered. Sacculi
... red. Sacculi prepared from lysozyme-treated strain 34 and additionally purified by electrophoresis were agglutinated by strain T14V. The specific coaggregation of Actinomyces viscosus T14 virulent (T14V) and Streptococcus sanguis 34 involves a binding protein (17, 18) on fimbriae (5, 6, 16) of A. viscosus T14V (3) and carbohydrate moieties (sites) on strain 34, presumably beta-galactosides or fucosides (4, 11, 17, 18) . Our efforts focussed on determining whether these sites were associated with the cell wall. A. viscosus T14V and S. sanguis 34 were cultured as described previously (18, 19) in Trypticase soy broth (TS; strain T14V and strain 34) or Todd-Hewitt broth (TH; strain 34 only) to an absorbance (650 nm) of 1.1 U. Specific coaggregation was quantitated by the turbidimetric assay (reaction volume of 1.0 ml) of McIntire et al. (18) , except that 25 mM Tris-hydrochloride (pH 8.2) replaced the phosphate buffer. Coaggregates of strain T14V and strain 34 were studied initially by phase-contrast and scanning electron microscopy and were very irregular in shape and varied markedly in size up to 523 by 318 p.m (D. S. Haberkorn, J. L. M. Foster, and V. M. Reusch, Jr., Abstr. Annu. Meet. Am. Soc. Microbiol. 1983, K153, p. 202). The interaction between cocci and strain T14V was not restricted to a specific portion of coccal cell surfaces, suggesting that active carbohydrate moieties are distributed all over the strain 34 surface. Despite a 10-fold-greater content of carbohydrate in their sacculi (19) , there was only a small difference in the ability of S. sanguis 34 grown in TS to coaggregate with strain T14V as compared with strain 34 grown in TH. Thus, the additional carbohydrate had little effect on the coaggrega-tion of strain 34 and its sacculi with strain T14V.