Adhesion of mutants streptococci to glass with and without a salivary coating as studied in a parallel-plate flow chamber

Abstract

Deposition and adhesion to glass with and without a salivary coating in a parallel-plate flow chamber were studied with four strains of mutans streptococci. Stationary-state adhesion of the strains to uncoated glass ranged from 0.3 x 10(6) cm-2 (Streptococcus rattus HG218) to 12.7 x 10(6) cm-2 (Streptococcus sobrinus HG1025) and generally decreased after saliva coating of the glass. The poor adhesion found for S. rattus HG218 to both uncoated and saliva-coated glass could be due to its relatively high negative surface-charge. Deposition efficiencies of all strains were greater than or equal to 1 for uncoated glass and decreased greatly after saliva coating of the glass. Possibly, adhesion to a saliva coating is less efficient and more time-consuming than that to uncoated glass, because stereochemical groups in the pellicle and on the cell surfaces may have to re-arrange before an effective interaction can occur. Desorption rates, measured 1000 s and 5000 s after the start of an experiment, decreased by a factor of ten upon a five-fold increase in contact time, indicative of a two-phase adhesion process. Of the four strains studied, only Streptococcus cricetus HG737 showed a minor positive cooperativity on saliva-coated glass, possibly mediated by surface appendages observed by transmission electron microscopy on negatively-stained cells. Retention of adhering bacteria was strain-dependent on uncoated glass, but was identical for all strains on saliva-coated glass, which suggests that the structure and composition of the pellicle may be more important with respect to the retention of adhering cells than the cell-surface properties themselves.